tag:theconversation.com,2011:/fr/topics/vaccine-booster-shots-104475/articlesVaccine booster shots – The Conversation2022-03-17T12:10:24Ztag:theconversation.com,2011:article/1790602022-03-17T12:10:24Z2022-03-17T12:10:24ZHow does the immune system mobilize in response to a COVID-19 infection or a vaccine? 5 essential reads<figure><img src="https://images.theconversation.com/files/452348/original/file-20220316-16-12d1gnq.jpg?ixlib=rb-1.1.0&rect=231%2C52%2C6774%2C4810&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The COVID-19 pandemic has taught most people more than they ever expected to know about immunology.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/coronavirus-structural-morphology-royalty-free-image/1215480593">Membio/iStock via Getty Images Plus</a></span></figcaption></figure><p>Heading into the third year of the COVID-19 pandemic, many of us have become amateur immunologists, having conversations at the dinner table and in the grocery store aisle about <a href="https://theconversation.com/how-mrna-vaccines-from-pfizer-and-moderna-work-why-theyre-a-breakthrough-and-why-they-need-to-be-kept-so-cold-150238">mRNA vaccines</a>, <a href="https://theconversation.com/will-omicron-the-new-coronavirus-variant-of-concern-be-more-contagious-than-delta-a-virus-evolution-expert-explains-what-researchers-know-and-what-they-dont-169020">variants</a>, <a href="https://theconversation.com/what-is-a-breakthrough-infection-6-questions-answered-about-catching-covid-19-after-vaccination-164909">breakthrough infections</a>, <a href="https://theconversation.com/how-long-does-protective-immunity-against-covid-19-last-after-infection-or-vaccination-two-immunologists-explain-177309">“waning” immunity</a>, <a href="https://theconversation.com/what-is-herd-immunity-a-public-health-expert-and-a-medical-laboratory-scientist-explain-170520">herd immunity</a>, <a href="https://theconversation.com/is-covid-19-here-to-stay-a-team-of-biologists-explains-what-it-means-for-a-virus-to-become-endemic-168462">endemic viruses</a>, <a href="https://theconversation.com/tense-decision-making-as-cdc-joins-fda-in-recommending-pfizer-booster-shot-for-65-and-up-people-at-high-risk-and-those-with-occupational-exposure-to-covid-19-168703">booster shots</a> and much more. </p>
<p>Many of the stories that we’ve published over the past two years here at The Conversation have stemmed from our own head-scratching questions that came up in our morning news meetings or were posed to us directly by curious readers. We sought out scholars who could take our readers on deep dives into immunology and virology to help demystify these sometimes confusing, conflicting and taxing science-based questions.</p>
<p>Here are five stories from The Conversation’s archives that highlight critical insights that we as editors and readers have gained thanks to COVID-19, and that will no doubt continue to be an important part of our pandemic lexicon. </p>
<h2>1. COVID-19 vaccines explained</h2>
<p>Understanding how vaccines can “trick” the body into mounting an effective immune response against a perceived or actual threat is one of the most fascinating aspects of immunology. “The most important thing to understand about vaccines is that they <a href="https://theconversation.com/what-happens-when-the-covid-19-vaccines-enter-the-body-a-road-map-for-kids-and-grown-ups-164624">teach your body how to gear up to fight an infection</a>, without your body having to deal with the infection itself,” writes <a href="https://scholar.google.com/citations?user=YpknwWcAAAAJ&hl=en">Glenn J. Rapsinski</a>, a pediatric infectious diseases fellow at the University of Pittsburgh Health Sciences. “In this way, vaccines help your body be prepared for invasions by germs that could otherwise make you very sick.”</p>
<p>Rapsinski explains how the COVID-19 vaccines available in the U.S. emulate the spike protein of SARS-CoV-2, the virus that causes COVID-19. “SARS-CoV-2 is a round virus, with bumps all over it – sort of like a baseball covered in golf tees. The bumps are the spike proteins.”</p>
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<a href="https://theconversation.com/what-happens-when-the-covid-19-vaccines-enter-the-body-a-road-map-for-kids-and-grown-ups-164624">What happens when the COVID-19 vaccines enter the body – a road map for kids and grown-ups</a>
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<h2>2. And then came breakthrough infections</h2>
<p>Soon after the relief that came with the widespread availability of vaccines in the spring of 2021, we were introduced to the idea of “breakthrough infections,” which were the rare cases in which fully vaccinated people got infected with COVID-19. </p>
<p>“<a href="https://theconversation.com/what-is-a-breakthrough-infection-6-questions-answered-about-catching-covid-19-after-vaccination-164909">Breakthrough infections</a> are a little more frequent than previously expected and are probably increasing because of growing dominance of the delta variant,” <a href="https://scholar.google.com/citations?user=F8vQ9xIAAAAJ&hl=en">Sanjay Mishra</a>, a cancer and vaccine researcher from Vanderbilt University, wrote in July 2021. “But infections in vaccinated people are still very rare and usually cause mild or no symptoms.” </p>
<p>Although breakthrough infections became far more common late in 2021, in part because of the emergence of the highly transmissible omicron variant – more on that down below – COVID-19 vaccines still continue to provide robust protection against the most severe forms of COVID-19 that lead to hospitalization and death.</p>
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Read more:
<a href="https://theconversation.com/what-is-a-breakthrough-infection-6-questions-answered-about-catching-covid-19-after-vaccination-164909">What is a breakthrough infection? 6 questions answered about catching COVID-19 after vaccination</a>
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<h2>3. The growing list of variants</h2>
<p>In 2020 and 2021, new strains of SARS-CoV-2 seemed to emerge faster than people could keep up with their Greek names. But by mid-2021, the highly transmissible delta variant had become the dominant strain in the U.S. and was responsible for the growing number of breakthrough infections. The continual emergence of variants was and is concerning, because it raises questions about how robust one’s immune protection will be from prior infections or from the COVID-19 vaccines, which were based on the original strain of the virus. </p>
<p>The delta variant was between 40% and 60% more transmissible than the alpha variant that it replaced and nearly <a href="https://theconversation.com/will-omicron-the-new-coronavirus-variant-of-concern-be-more-contagious-than-delta-a-virus-evolution-expert-explains-what-researchers-know-and-what-they-dont-169020">twice as transmissible as the original SARS-CoV-2</a> virus, wrote <a href="https://scholar.google.com/citations?user=dqahf8oAAAAJ&hl=en">Suresh V. Kuchipudi</a>, a professor of emerging infectious diseases at Penn State. </p>
<p>But then, of course, came omicron, which was even more contagious than delta, thanks in part to its high number of mutations. “Omicron is very unusual in that it is by far the most heavily mutated variant yet of SARS-CoV-2, the virus that causes COVID-19,” Kuchipudi explained. “The omicron variant has 50 mutations overall, with 32 mutations on the spike protein alone. The spike protein – which forms protruding knobs on the outside of the SARS-CoV-2 virus – helps the virus adhere to cells so that it can gain entry.”</p>
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Read more:
<a href="https://theconversation.com/will-omicron-the-new-coronavirus-variant-of-concern-be-more-contagious-than-delta-a-virus-evolution-expert-explains-what-researchers-know-and-what-they-dont-169020">Will omicron – the new coronavirus variant of concern – be more contagious than delta? A virus evolution expert explains what researchers know and what they don't</a>
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<h2>4. Putting ‘endemic’ viruses into context</h2>
<p>At some point in 2021 – the year is one big blur – we entered a phase of the pandemic where it became clear that we were stuck with COVID-19 for the foreseeable future. For many people, there was a mental shift from the assumption that we could eradicate the coronavirus that causes COVID-19 through vaccination, into the slow realization that it just wasn’t going away. Virologists and other researchers began using the term “endemic” to describe the way that some viruses can fade away but still maintain a low level of transmission in a community. </p>
<p><a href="https://scholar.google.com/citations?user=XY7DNtgAAAAJ&hl=en">Sara Sawyer</a>, <a href="https://experts.colorado.edu/display/fisid_166880">Arturo Barbachano-Guerrero</a> and <a href="https://scholar.google.com/citations?user=l2lpnYkAAAAJ&hl=en">Cody Warren</a>, a team of virologists and immunologists <a href="https://theconversation.com/is-covid-19-here-to-stay-a-team-of-biologists-explains-what-it-means-for-a-virus-to-become-endemic-168462">from the University of Colorado Boulder explain</a> that SARS-CoV, the coronavirus that set off the SARS pandemic in 2003, was less contagious than SARS-CoV-2 and was brought under control relatively quickly by speedy public health measures that ultimately drove the virus extinct. </p>
<p>On the other hand, they wrote, “pandemic viruses may also gradually settle into a relatively stable rate of occurrence, maintaining a constant pool of infected hosts capable of spreading the virus to others.” Such viruses are said to be “endemic” – as will likely become the case with the coronavirus that causes COVID-19.</p>
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<a href="https://theconversation.com/is-covid-19-here-to-stay-a-team-of-biologists-explains-what-it-means-for-a-virus-to-become-endemic-168462">Is COVID-19 here to stay? A team of biologists explains what it means for a virus to become endemic</a>
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<h2>5. Immune defenses shift over time</h2>
<p>As 2021 waned, so – apparently – did protective antibodies against COVID-19. Researchers began to learn more about how the immune response shifts in the months following COVID-19 infection or vaccination. And it became clear that over time, people became more vulnerable to getting reinfected or having a breakthrough infection following vaccination – in part because of the emergence of variants.</p>
<p>But antibodies are only <a href="https://theconversation.com/how-long-does-protective-immunity-against-covid-19-last-after-infection-or-vaccination-two-immunologists-explain-177309">part of the immune system’s protective defense</a>, explain <a href="https://scholar.google.com/citations?user=jJVj3sUAAAAJ&hl=en">Prakash Nagarkatti</a> and <a href="https://scholar.google.com/citations?user=af7TahQAAAAJ&hl=en">Mitzi Nagarkatti</a>, a husband-and-wife team of immunologists from the University of South Carolina. </p>
<p>“Throughout the COVID-19 pandemic, the public has widely and mistakenly believed that antibodies provide the bulk of protective immunity, while not recognizing the important role of killer T cells,” they write. “This is in part because antibodies are easy to detect, whereas killer T-cell detection is complex and involves advanced technology. When antibodies fail, it is the killer T cells that are responsible for preventing the more severe outcomes of COVID-19, such as hospitalization and death.”</p>
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Read more:
<a href="https://theconversation.com/how-long-does-protective-immunity-against-covid-19-last-after-infection-or-vaccination-two-immunologists-explain-177309">How long does protective immunity against COVID-19 last after infection or vaccination? Two immunologists explain</a>
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<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/179060/count.gif" alt="The Conversation" width="1" height="1" />
The COVID-19 pandemic has brought immunology terms that are typically relegated to textbooks into our everyday vernacular. These stories helped us make sense of the ever-evolving science.Amanda Mascarelli, Senior Health and Medicine EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1778262022-03-16T19:28:41Z2022-03-16T19:28:41ZFlu, COVID and flurona: what we can and can’t expect this winter<figure><img src="https://images.theconversation.com/files/452341/original/file-20220316-28-dvj9zq.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/black-woman-feeling-sick-seasonal-flu-1201292887">Shutterstock</a></span></figcaption></figure><p>When it comes to respiratory viruses, COVID has been our greatest concern over the past two winters. So you might feel some aspects of <em>déjà vu</em> as winter 2022 approaches in Australia. </p>
<p>But this year is different. With relaxed public health measures and the opening of international borders, we will likely see a rise in flu cases. This is on top of a predicted rise in COVID.</p>
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<p>The potential double-whammy has prompted the federal government to announce <a href="https://www.abc.net.au/news/2022-03-11/health-package-to-target-expected-covid-and-flu-spike/100901242">A$2.1 billion</a> to target these expected spikes. The funding has <a href="https://www.health.gov.au/ministers/the-hon-greg-hunt-mp/media/canberra-press-conference-11-march-2022-on-kimberley-kitching-japanese-encephalitis-extensions-to-vaccinationbooster-plan-winter-preparedness-plan-for-covid-and-flu">been earmarked</a> for measures including vaccination, testing and measures to protect aged care.</p>
<p>Here’s what to expect and how to protect yourself ahead of winter.</p>
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Read more:
<a href="https://theconversation.com/heres-why-you-might-need-a-4th-covid-vaccine-dose-this-winter-177811">Here's why you might need a 4th COVID vaccine dose this winter</a>
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<h2>Why can we expect more flu?</h2>
<p>The main reason behind the expected rise in flu in 2022 is the opening of Australia’s international borders. </p>
<p>Tourists and returning residents can arrive without quarantining, provided they have the required COVID vaccinations and have had a COVID test beforehand. However, new arrivals don’t have to be tested for the flu virus, which they may inadvertently bring with them.</p>
<p>Flu, a little like COVID, can be spread by infected others before symptoms arise or even if symptoms don’t appear, something we regularly see in children. So once flu arrives, it will inevitably spread, regardless of whether we use masks, hand sanitiser or other measures.</p>
<p>In the past two years, for instance, we’ve seen large outbreaks of <a href="https://www.health.nsw.gov.au/Infectious/covid-19/Documents/covid-19-surveillance-report-20220107.pdf">other common respiratory viruses</a>. These include <a href="https://pubmed.ncbi.nlm.nih.gov/33735388/">respiratory syncytial virus</a>, <a href="https://www.health.nsw.gov.au/Infectious/covid-19/Documents/covid-19-surveillance-report-20220107.pdf">human metapneumovirus</a>, <a href="https://www.cdc.gov/adenovirus/about/symptoms.html">adenoviruses</a> and <a href="https://www.healthychildren.org/English/health-issues/conditions/ear-nose-throat/Pages/Rhinovirus-Infections.aspx">rhinovirus</a>. We’ve seen these even with strict COVID measures in Victoria, New South Wales and Queensland during 2020-2021.</p>
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Read more:
<a href="https://theconversation.com/we-can-expect-more-colds-and-flu-as-covid-restrictions-lift-5-germs-to-look-out-for-170263">We can expect more colds and flu as COVID restrictions lift. 5 germs to look out for</a>
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<h2>How bad will it get?</h2>
<p>It’s highly likely we’ll see COVID and influenza circulating at the same time this winter. But less certain is the more catastrophic predictions in the media of a so-called twindemic or syndemic.</p>
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<p>COVID is more likely to persist and increase during the winter, and sometime during this period influenza will pop up. But we’re uncertain about the details.</p>
<p>Will flu be mild or more concerning in 2022? Will we see a rise in cases during the usual June-September period, peaking normally in August? The answers to these questions rely on history, the current situation and a good deal of speculation.</p>
<p>History tells us that after two seasons of low or no influenza circulating, we should expect a more severe season. That’s because the majority of people are not vaccinated against influenza each year and peoples’ natural immunity after infection will have waned.</p>
<p>However, <a href="https://www.who.int/teams/global-influenza-programme/surveillance-and-monitoring/influenza-updates/current-influenza-update">current evidence</a> argues against this. In the Northern Hemisphere, there have been low levels of flu circulating in most countries, with shorter outbreaks, compared with pre-pandemic years. </p>
<p>We’ve also seen a number of countries in the Southern Hemisphere – including <a href="https://www.who.int/tools/flunet">South Africa, Brazil and Chile</a> – having out-of-season flu outbreaks, during their 2021-2022 summer.</p>
<p>So this may mean the timing of Australia’s normal influenza season might be delayed until spring or even later in 2022.</p>
<h2>Will I get ‘flurona’?</h2>
<p>We may also see dual infections – when someone has COVID and influenza at the same time – sometimes dubbed “flurona”.</p>
<p>While this has occurred, the rates of dual infections globally have been low. Generally, <a href="https://www.frontiersin.org/articles/10.3389/fmed.2021.681469/full">under 1% of people</a> with COVID also have influenza at the same time. Even with dual infections, people do not seem to be sicker than if they had COVID alone.</p>
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<p>We’ll have a better idea of how many people will be infected with both viruses at once with the use of broader laboratory tests now available at many sites. These so called <a href="https://www.health.gov.au/ministers/the-hon-greg-hunt-mp/media/canberra-press-conference-11-march-2022-on-kimberley-kitching-japanese-encephalitis-extensions-to-vaccinationbooster-plan-winter-preparedness-plan-for-covid-and-flu">multiplex tests</a> will detect a range of respiratory diseases, including COVID and flu, in a single test.</p>
<p>Fortunately, there is no way a new “hybrid virus” can emerge containing parts of SARS-CoV-2 (the virus that causes COVID) and the influenza virus in people with dual infections. These are distinct viruses that cannot combine.</p>
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Read more:
<a href="https://theconversation.com/alpha-then-delta-and-now-omicron-6-questions-answered-as-covid-19-cases-once-again-surge-across-the-globe-174703">Alpha then delta and now omicron – 6 questions answered as COVID-19 cases once again surge across the globe</a>
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<h2>How can I protect myself?</h2>
<p>Despite the uncertainties around flu in Australia in 2022, the best way to protect yourself is to get your flu vaccine.</p>
<p>Everyone is susceptible to flu, no matter your age, health or lifestyle. However, some age groups and some people with underlying disease are likely to suffer more severe consequences if infected with influenza. </p>
<p>These include young children (especially those under two years old), people aged 65 and over, pregnant women, people with chronic lung and heart disease, those with asthma, diabetes and people who are obese.</p>
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Read more:
<a href="https://theconversation.com/you-cant-get-influenza-from-a-flu-shot-heres-how-it-works-118916">You can't get influenza from a flu shot – here's how it works</a>
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<p>Different flu vaccines target different age groups with different formulations. These vaccines have a <a href="https://ausvaxsafety.org.au/safety-data/influenza-vaccine">proven safety record</a> and usually only cause very mild reactions, such as soreness at the injection site, mild fever or headache. These may last for a 12-24 hours and are easily treated with paracetamol or similar medications.</p>
<p><a href="https://www.health.gov.au/health-topics/immunisation/when-to-get-vaccinated/national-immunisation-program-schedule">Flu vaccines are free</a> for children aged six months to under five years of age, people aged 65 or older, pregnant women and all Aboriginal and Torres Strait Islander people six months and older. People not eligible for free vaccines can still get them via their GP or some pharmacies.</p>
<p>This year you won’t have to schedule different visits for your influenza and COVID vaccinations. If needed, you can get them <a href="https://www.health.gov.au/sites/default/files/documents/2022/02/atagi-advice-on-seasonal-influenza-vaccines-in-2022.pdf">at the same time</a>.</p>
<p>Influenza vaccines will be available from late March and <a href="https://www.cdc.gov/flu/prevent/keyfacts.htm">will provide protection</a> for at least 6-12 months. While these vaccines are not perfect they help prevent infection and the more serious consequences of the flu, such as hospitalisation and even death. So in April to May this year, as the cool days and nights return, think about booking in and getting your flu shot.</p><img src="https://counter.theconversation.com/content/177826/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Barr owns shares in a vaccine producing company. His Centre receives funding from the Australian Government Department of Health as well as a number of commercial pharmaceutical companies.</span></em></p>Flu vaccines will soon be available. And this year, you can get your COVID shot at the same time.Ian Barr, Deputy Director, WHO Collaborating Centre for Reference and Research on InfluenzaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1763592022-02-04T03:29:41Z2022-02-04T03:29:41Z16-17 year olds can now get their COVID boosters. Why not younger children?<figure><img src="https://images.theconversation.com/files/444210/original/file-20220203-25-m4sceg.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/vaccinated-girl-teenager-teen-mixed-race-2025352361">Shutterstock</a></span></figcaption></figure><p>Adolescents aged 16-17 are now eligible to receive their Pfizer vaccine booster, following the <a href="https://www.health.gov.au/news/atagi-recommendations-for-use-of-pfizer-covid-19-vaccine-as-a-booster-dose-in-adolescents-aged-16-17-years">recommendation</a> earlier this week from the Australian Technical Advisory Group on Immunisation (ATAGI).</p>
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<p>This move has been prompted by the <a href="https://theconversation.com/should-i-get-my-covid-vaccine-booster-yes-it-increases-protection-against-covid-including-omicron-172965">rise of Omicron</a> and reduced immunity after two vaccine doses.</p>
<p>It’s also the next step in the likely future expansion of booster doses to younger adolescents.</p>
<p>Here’s what you need to know before <a href="https://www.health.gov.au/initiatives-and-programs/covid-19-vaccines/getting-your-vaccination/booster-doses">booking your 16-17 year old for their booster</a>, and why younger children are not yet eligible.</p>
<h2>What’s been recommended?</h2>
<p>ATAGI’s recommendation to extend Pfizer booster doses to 16-17 year olds this week follows <a href="https://www.tga.gov.au/media-release/pfizers-covid-19-vaccine-comirnaty-provisionally-approved-use-booster-individuals-aged-16-17-years-old">regulatory approval</a> from the Therapeutic Goods Administration (TGA) in late January.</p>
<p>This means an estimated <a href="https://www.health.gov.au/ministers/the-hon-greg-hunt-mp/media/eligible-australian-kids-16-can-now-get-a-booster">370,000 Australians aged 16-17</a> are eligible to receive their Pfizer booster vaccine from three months after their second dose.</p>
<p>Presently, the Pfizer vaccine is the only one registered as a booster for this age group.</p>
<p>Those under 16 when they received their second dose but have since turned 16 are also eligible. </p>
<p>Those 16-17 year olds who are severely immunocompromised – for instance, with weakened immune systems due to cancer treatment – <a href="https://www.health.gov.au/resources/publications/atagi-recommendations-on-the-use-of-a-third-primary-dose-of-covid-19-vaccine-in-individuals-who-are-severely-immunocompromised">are recommended</a> to have three primary doses, and three months later, have their booster (fourth) dose.</p>
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Read more:
<a href="https://theconversation.com/if-my-child-or-i-have-covid-when-can-we-get-our-vaccine-or-booster-shot-174690">If my child or I have COVID, when can we get our vaccine or booster shot?</a>
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<h2>Why Omicron changes things</h2>
<p>The <a href="https://www.unicef.org/coronavirus/what-we-know-about-omicron-variant">more transmissible</a> Omicron variant can still infect people who have <a href="https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-49-Omicron/">already been infected</a> with SARS-CoV-2 (the virus that causes COVID), or who have had two vaccine doses.</p>
<p>For the vast majority of older adolescents, these so-called <a href="https://theconversation.com/what-we-know-now-about-covid-immunity-after-infection-including-omicron-and-delta-variants-175653">breakthrough infections</a> are mild and very unlikely to lead to hospitalisation.</p>
<p><a href="https://www.health.nsw.gov.au/Infectious/covid-19/Documents/covid-19-surveillance-report-20220201.pdf">Data from New South Wales</a> during the Omicron period (November 26, 2021 to January 15, 2022) shows of 71,786 PCR-confirmed cases in adolescents (aged 10-19 years) only 191 cases (under 1%) required hospitalisation.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1487000248878723072"}"></div></p>
<p>Then there’s the issue of waning immunity following the initial two doses.</p>
<p>Real-world data from adults in the United Kingdom shows four months after two Pfizer doses there is <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1050721/Vaccine-surveillance-report-week-4.pdf">modest protection</a> against Omicron infection (<a href="https://www.health.gov.au/news/atagi-recommendations-for-use-of-pfizer-covid-19-vaccine-as-a-booster-dose-in-adolescents-aged-16-17-years">vaccine effectiveness 0-34%</a>).</p>
<p>However, a Pfizer booster dose <a href="https://www.health.gov.au/news/atagi-recommendations-for-use-of-pfizer-covid-19-vaccine-as-a-booster-dose-in-adolescents-aged-16-17-years">quickly improves protection</a> against Omicron. Vaccine effectiveness increases to 54-76% within two to four weeks after a booster.</p>
<p>It is important to note that studies of the effectiveness of booster doses specifically in adolescents aged 16-17 against Omicron are not yet available. However, this is likely to be comparable to that for young adults.</p>
<p>The booster dose has several aims. It not only reduces the chances of getting infected in the first place, it reduces the severity of infection in an individual if they do. This means people are less likely to have to take time off school or work.</p>
<p>Adolescents are also a very mobile social group and there may be a potential benefit of a booster vaccine in reducing community transmission. If a booster vaccine reduces your chances of infection it follows it could then reduce community transmission. But <a href="https://jamanetwork.com/journals/jama/fullarticle/2788105">more research is needed</a> to confirm if this occurs for Omicron.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-vaccine-doses-differ-for-babies-kids-teens-and-adults-an-immunologist-explains-how-your-immune-system-changes-as-you-mature-168708">Why vaccine doses differ for babies, kids, teens and adults – an immunologist explains how your immune system changes as you mature</a>
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</em>
</p>
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<h2>How safe are boosters for adolescents?</h2>
<p><a href="https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2022-01-05/02-COVID-Su-508.pdf">Safety data from the United States</a> indicates Pfizer booster doses in adolescents have a similar profile to that seen after a Pfizer second dose.</p>
<p><a href="https://ausvaxsafety.org.au/all-participants/pfizer-covid-19-vaccine-safety-data-all-participants">Early data</a> on booster doses from Australia’s active safety surveillance system also supports the safety of a Pfizer booster dose in adults. In over 600,000 surveys, the most common reported reactions include pain, redness and swelling at the injection site, tiredness, headache and muscle aches.</p>
<p>We also know that both Pfizer (and Moderna) COVID-19 vaccines have rarely been associated with <a href="https://theconversation.com/myocarditis-covid-19-is-a-much-bigger-risk-to-the-heart-than-vaccination-174580">myocarditis</a>, a treatable <a href="https://www.health.gov.au/resources/publications/covid-19-vaccination-guidance-on-myocarditis-and-pericarditis-after-mrna-covid-19-vaccines">inflammation of the heart</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1486839938997911552"}"></div></p>
<p>In studies in the US, <a href="https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-10-20-21/07-COVID-Su-508.pdf">the estimated myocarditis rate</a> in young males aged 16-17 after the second Pfizer dose was 6.9 per 100,000 doses.</p>
<p>Australian <a href="https://www.tga.gov.au/periodic/covid-19-vaccine-weekly-safety-report-03-02-2022">data from the TGA show</a> estimated rates of likely myocarditis in males aged 12-17 years of 10.9 per 100,000 doses after the second dose of Pfizer vaccine. </p>
<p>As the booster vaccine program rolls out to 16-17 year olds, the TGA and state/territory health departments will closely monitor any adverse events.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/covid-vaccines-have-been-developed-in-record-time-but-how-will-we-know-theyre-safe-153888">COVID vaccines have been developed in record time. But how will we know they're safe?</a>
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</p>
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<h2>Why can’t younger kids get their booster?</h2>
<p>The <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html">US now recommends</a> booster doses for everyone aged 12 and older, from five months after the second dose.</p>
<p>It is likely Australia will also see a recommendation for booster doses in younger adolescents (12-15 year olds) and potentially younger children (5-11 year olds) in the future.</p>
<p>However, for now, our focus is on <a href="https://www.health.gov.au/sites/default/files/documents/2022/02/covid-19-vaccine-rollout-update-3-february-2022_0.pdf">rolling out the two primary doses</a> in 12-15 year olds before considering any booster doses in this age group.</p>
<p>In the meantime, Australia will be closely monitoring data from the US and other countries before expanding the booster program to younger children. This will include:</p>
<ul>
<li><p>safety data, with a focus on the risk of myocarditis</p></li>
<li><p>looking at the best interval between primary and booster doses</p></li>
<li><p>effectiveness data, with a focus on breakthrough infections and their severity.</p></li>
</ul>
<p>Pfizer, or other vaccine manufacturers, would need to seek regulatory approval for boosters in younger age groups, and provide safety and effectiveness data.</p>
<p>Australia would also closely watch for the emergence of any new viral variants when considering the need to expand the booster program.</p><img src="https://counter.theconversation.com/content/176359/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Wood has received funding from the NHMRC for a Career Development Fellowship. He holds a Churchill Fellowship awarded in 2019.</span></em></p>It’s too soon to recommend booster shots for younger children. But we can watch what’s happening in the US, where children as young as 12 are receiving theirs.Nicholas Wood, Associate Professor, Discipline of Childhood and Adolescent Health, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1761442022-02-02T19:11:37Z2022-02-02T19:11:37ZNew Zealand’s border quarantine has intercepted thousands of COVID cases, but is it time to retire the flawed system?<figure><img src="https://images.theconversation.com/files/443912/original/file-20220201-21-115iauw.jpg?ixlib=rb-1.1.0&rect=41%2C174%2C5505%2C3517&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Lynn Grieveson /Newsroom via Getty Images</span></span></figcaption></figure><p>The <a href="https://www.rnz.co.nz/news/national/460660/pregnant-journalist-charlotte-bellis-offered-a-place-in-miq">controversy</a> surrounding New Zealand journalist Charlotte Bellis, who has now accepted a place in border quarantine after initially seeking refuge in Afghanistan when her first application was declined, has highlighted confusion and concern over New Zealand’s managed isolation and quarantine (MIQ) system.</p>
<p>Cabinet ministers are currently discussing changes to MIQ as part of a plan to reopen New Zealand’s borders, expected to be announced later today. This will update a <a href="https://www.rnz.co.nz/news/national/456430/covid-19-major-miq-changes-from-early-next-year">staged timeline</a> announced late last year, which was pushed back when the Omicron variant emerged overseas.</p>
<p>Since New Zealand’s MIQ system was established at the start of the COVID-19 pandemic, it has intercepted more than 2000 cases at the border. Over half of these have been found in the two months since the start of December, following Omicron’s rise to global dominance. </p>
<p>If New Zealand had removed the requirement for international arrivals to go through MIQ last year, we would almost certainly have faced a large Omicron wave during December and January, just as happened in many Australian states. Does this matter, given we are now facing an Omicron wave anyway? </p>
<p>The answer is a clear yes. </p>
<p>By delaying the start of the Omicron outbreak New Zealand has bought valuable time to prepare. This has allowed for the build-up of supplies of <a href="https://www.beehive.govt.nz/release/government-secures-extra-36-million-rapid-antigen-tests">rapid antigen tests</a>, which will be needed when case numbers take off, and work on <a href="https://www.beehive.govt.nz/release/5000-portable-air-cleaners-schools-their-way">improved ventilation in schools</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1488299737405018113"}"></div></p>
<p>It has also enabled us to reduce the number of Delta cases to very low levels, lowering the chances of a “<a href="https://www.stuff.co.nz/national/explained/127440590/covid19-the-nsw-omicron-outbreak-is-not-what-you-think">dual epidemic</a>” with Omicron dominating cases but Delta adding significant extra demand on hospitals and intensive care units. </p>
<h2>Boosted and better prepared</h2>
<p>We have also learnt a lot about Omicron itself in the past two months, allowing us to adjust our response. But most crucially, the delay tactics have provided time to increase collective immunity by rolling out booster doses and starting vaccination of 5-11-year-olds. </p>
<p>Over 1.3 million New Zealanders have <a href="https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-vaccine-data">now been boosted</a>, including some of our higher-risk groups. And about one in three 5-11-year-olds has had their first dose. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-most-challenging-phase-of-the-omicron-outbreak-is-yet-to-come-but-new-zealand-may-be-better-prepared-than-other-countries-175819">The most challenging phase of the Omicron outbreak is yet to come, but New Zealand may be better prepared than other countries</a>
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<p>Boosters are essential for providing high levels of protection against serious illness with Omicron. Data from the <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1050721/Vaccine-surveillance-report-week-4.pdf">UK Health Security Agency</a> estimate that, about three months after the second dose, the risk of being hospitalised with COVID-19 is about half that of an unvaccinated person. After a booster, this drops to about one tenth of the risk of an unvaccinated person. </p>
<figure class="align-center ">
<img alt="Queue of people waiting outside a vaccination centre." src="https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443915/original/file-20220201-27-1bhrb2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">More than a million New Zealanders have now received a booster.</span>
<span class="attribution"><span class="source">Kai Schwoerer/Getty Images</span></span>
</figcaption>
</figure>
<p>New Zealand needs to keep up the momentum of the booster programme and childhood vaccine rollout. Without the additional immunity boosters have given older age groups over the last two months, we would now be facing significantly higher levels of severe illness and death than we are.</p>
<h2>Does New Zealand still need MIQ?</h2>
<p>There are currently 100-200 COVID-19 cases in the community each day and 40-70 cases in MIQ. If we removed the requirement for people to quarantine, we would very likely see a big increase in the number of people travelling to New Zealand.
This could easily translate into several hundred cases per day arriving at the border. </p>
<p>Our <a href="https://www.sciencedirect.com/science/article/pii/S2468042721000877">recent modelling</a> shows home isolation and testing requirements could reduce the risk of community transmission from international arrivals by up to 80%. But even in the best-case scenario, we would be adding about a hundred new chains of transmission to the community outbreak every day. </p>
<p>These transmission chains would grow exponentially, significantly accelerating the outbreak and adding to the pressure on our contact tracing and healthcare systems. </p>
<p>For now, MIQ is continuing to do an important job of slowing down the outbreak and buying us more time. This is an essential part of New Zealand’s strategy to flatten the curve and avoid overwhelming healthcare capacity.</p>
<p>Once there are several thousand cases per day, adding a few hundred border cases will start to become less important. Relaxing border restrictions at this point would make sense: it would be reasonable to accept a higher level of risk at the border, provided no new variant of concern emerges. </p>
<p>MIQ capacity could be used more effectively for high-risk community cases who are unable to isolate at home. </p>
<h2>The future of MIQ</h2>
<p>Over the course of the pandemic, there have been four notable community outbreaks that likely originated from MIQ facilities (August 2020, February 2021, August 2021 and the current Omicron outbreak). There have also been several near misses, many of which were prevented from causing a larger outbreak by routine testing of border workers. </p>
<p>MIQ has been one of the main reasons New Zealand has managed to avoid the <a href="https://www.economist.com/graphic-detail/coronavirus-excess-deaths-tracker">massive death tolls</a> seen in other countries.</p>
<p>Thanks to highly effective vaccines, New Zealand has now moved away from the elimination strategy. But SARS-CoV-2 continues to surprise us with new variants. </p>
<p>Although Omicron is <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/hospitalisation-risk-omicron-around-one-third-delta-uk-analysis-shows-2021-12-31/">less severe</a> than the Delta variant, it is <a href="https://www.stuff.co.nz/national/explained/127622391/covid19-nz-is-it-really-a-good-idea-to-call-omicron-mild">not mild</a> and still poses a major threat to health systems because of the sheer number of cases it can cause. Delaying the arrival of Omicron into New Zealand has likely saved lives.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-does-omicron-appear-to-cause-less-severe-disease-than-previous-variants-174495">Why does omicron appear to cause less severe disease than previous variants?</a>
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</em>
</p>
<hr>
<p>The New Zealand government faces some tough decisions. There is an understandable desire to make it easier for people to cross the border, but it is unlikely Omicron will be the last variant this pandemic throws at us. </p>
<p>Unfortunately, there’s no guarantee the next variant won’t be more severe or better able to evade existing immunity. If a dangerous new variant does emerge, the ability to quickly stand up MIQ facilities once again could prove invaluable.</p><img src="https://counter.theconversation.com/content/176144/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Plank is affiliated with the University of Canterbury and is funded by the New Zealand Government for research on Covid-19.</span></em></p><p class="fine-print"><em><span>Audrey Lustig is affiliated with Manaaki Whenua Landcare Research and receives funding from Te Pūnaha Matatini, New Zealand's Centre of Research Excellence in complex systems. </span></em></p><p class="fine-print"><em><span>Giorgia Vattiato receives funding from the University of Auckland, and has previously received funding from Te Punaha Matatini.</span></em></p><p class="fine-print"><em><span>Shaun Hendy is affiliated with the University of Auckland and has received funding from the Ministry of Business, Innovation and Employment (MBIE) and Te Pūnaha Matatini, New Zealand's Centre of Research Excellence in complex systems.</span></em></p>New Zealand’s system of managed quarantine at the border may soon be less important, but we could well need to stand it up again quickly if a new COVID-19 variant emerges.Michael Plank, Professor in Applied Mathematics, University of CanterburyAudrey Lustig, Research scientist, Manaaki Whenua - Landcare ResearchGiorgia Vattiato, University of CanterburyShaun Hendy, Professor of Physics, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1747032022-01-21T13:42:45Z2022-01-21T13:42:45ZAlpha then delta and now omicron – 6 questions answered as COVID-19 cases once again surge across the globe<figure><img src="https://images.theconversation.com/files/440917/original/file-20220114-16-yxousj.jpg?ixlib=rb-1.1.0&rect=468%2C100%2C10694%2C4318&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The list of SARS-CoV-2 variants – each with its own unique qualities that give it an edge – just keeps growing.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/alpha-beta-gamma-delta-omicron-covid-variant-royalty-free-image/1361940125?adppopup=true">Matt Anderson Photography/Moment via Getty Images</a></span></figcaption></figure><p><em>Editor’s note: The <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/omicron-variant.html">omicron variant</a> of SARS-CoV-2, the virus that causes COVID-19, has fueled a <a href="https://www.cnbc.com/2022/01/12/who-says-omicron-cases-are-off-the-charts-as-global-infections-set-new-records.html">rapid surge in cases globally</a>. We asked a team of virologists and immunologists from the University of Colorado Boulder to weigh in on some of the pressing questions that people are asking about the new variant.</em></p>
<h2>How is omicron different from previous variants?</h2>
<p>There are two key differences between omicron and previous variants of the SARS-CoV-2 virus that emerged in late 2019. Early data suggests that <a href="https://doi.org/10.1101/2022.01.11.22269045">omicron cases are milder</a> than infections caused by the delta variant. On the flip side, omicron is far more transmissible – meaning it spreads easier – than previous variants. It can be confusing to think about the overall effects of a milder virus that is also far more infectious.</p>
<p>When the delta variant became dominant and displaced alpha in the summer of 2021, it managed to do so because it was <a href="https://asm.org/Articles/2021/July/How-Dangerous-is-the-Delta-Variant-B-1-617-2">between 40% and 60% more transmissible</a>. Now, the omicron variant is even <a href="https://www.npr.org/sections/goatsandsoda/2021/12/15/1064597592/a-tantalizing-clue-to-why-omicron-is-spreading-so-quickly">more transmissible than delta</a>.</p>
<p>It’s difficult to put numbers around how intrinsically more transmissible one variant is than another, because human behaviors and vaccination percentages are constantly in flux. Those factors, together with transmissibility, affect how a virus fares in a population. </p>
<p>In comparison with the original strain of SARS-CoV-2, omicron contains <a href="https://covariants.org/variants/21K.Omicron">72 mutations</a> throughout its genome. Some of these mutations account for the complex new features that characterize this variant. Half of those changes are in the spike protein, the critical surface protein that enables the virus to latch on and infect cells. It is also the key virus feature that is recognized by the human immune system. </p>
<h2>Why is omicron spreading so quickly?</h2>
<p>Initial studies suggest that omicron is more effective at reproducing in the upper airways, including <a href="https://doi.org/10.1101/2021.12.31.474653">the nose</a>, <a href="https://doi.org/10.1101/2021.12.22.21268246">throat</a> and <a href="https://doi.org/10.1038/s41591-021-01296-8">mouth</a>, than earlier variants, making it more similar to a common cold virus. If data from these preliminary studies holds up, then it may help explain omicron’s high transmissibility: Viruses replicating in the upper airways <a href="https://www.nytimes.com/2021/12/31/health/covid-omicron-lung-cells.html">may spread more easily</a>, although the reasons for this are not completely understood.</p>
<p>In addition, omicron is often able to <a href="https://doi.org/10.1038/s41586-021-04385-3">evade existing immunity</a> long enough to start an infection, cause symptoms and transmit onward to the next person. This explains why reinfections and vaccine <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/why-measure-effectiveness/breakthrough-cases.html">breakthrough infections</a> seem to be more common with omicron.</p>
<p>Those properties, and the timing of this variant emerging during the holiday season, resulted in the extraordinary surge in COVID-19 infections in the U.S. Add in wintertime – which brought people indoors – along with <a href="https://www.scientificamerican.com/article/how-we-can-deal-with-pandemic-fatigue/">pandemic fatigue</a>, and you have the perfect storm for rapid transmission. </p>
<p>The good news is that vaccination and vaccine boosters nevertheless <a href="https://www.research.ed.ac.uk/en/publications/severity-of-omicron-variant-of-concern-and-vaccine-effectiveness-">provide good protection</a> against severe disease and hospitalization. But given the current number of cases, that still means a lot of illnesses, hospitalizations and deaths in the weeks to come. </p>
<figure class="align-center ">
<img alt="A computer-generated image of the omicron variant." src="https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441625/original/file-20220119-17-16kkmdo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Omicron contains a large number of mutations and is much more transmissible than earlier variants of the SARS-CoV-2 virus.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/omicron-variant-of-coronavirus-or-covid-19-a-royalty-free-image/1359621511?adppopup=true">Uma Shankar sharma/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>Could omicron move the population closer to herd immunity?</h2>
<p><a href="https://theconversation.com/what-is-herd-immunity-a-public-health-expert-and-a-medical-laboratory-scientist-explain-170520">Herd immunity</a> occurs when enough people have immunity to a virus that it no longer spreads well. It is only possible when two conditions are met. First, a large fraction of the population must be vaccinated or recovered from prior infection. Second, vaccination or prior infection must confer enough immunity to block or slow future infections. Will vaccination campaigns, combined with widespread omicron infection, be enough to bring herd immunity?</p>
<p>Three issues complicate the hope of achieving a long-term herd immunity after omicron. The first is that immunity naturally wanes over time, regardless of whether it comes from a vaccine or prior infection. It is not yet clear how long after infection or vaccination immunity to this virus lasts, since SARS-CoV-2 has been infecting humans for only two years. Eventually, controlled studies will be able to determine this.</p>
<p>Second, children younger than age 5 are not yet eligible for COVID-19 vaccines, and new susceptible children are born every day. So, until all age groups are eligible for vaccination, there will likely be ongoing transmission in kids. </p>
<p>And third, we can’t rule out that new variants could escape existing immunity. As <a href="https://doi.org/10.1101/2022.01.05.22268782">omicron has shown</a>, infection with one variant doesn’t guarantee protection against infection by future variants. </p>
<p>Together, these three factors suggest that even if a large enough fraction of the population recovers from omicron, long-term herd immunity is unlikely. These are the same reasons that humans never achieve long-lasting herd immunity to influenza and have to get a new flu vaccine each year.</p>
<p>It’s important to remember that, with all variants to date, most of the people who are hospitalized for COVID-19 <a href="https://coronavirus.health.ny.gov/covid-19-breakthrough-data">are unvaccinated</a>. This shows that vaccines are an effective tool for reducing disease severity and can be beneficial even against new variants. </p>
<h2>Where do new variants like omicron come from?</h2>
<p>When viruses make more copies of themselves inside of human cells, they make mistakes in that process – mutations – that alter their genetic code. Most of these mutations will not be beneficial to the virus. However, in some instances, a virus hits on a jackpot of one or more beneficial mutations that fuel its spread through a population. The alpha variant possessed some mutations in the spike protein that made it <a href="https://doi.org/10.7554/eLife.69091">easier for viruses to infect cells</a>. The delta variant had additional mutations that <a href="https://www.nature.com/articles/d41586-021-02275-2">improved viral spread</a>. Omicron, with its staggering number of mutations, is a true oddity. It’s rare for a coronavirus to rapidly accumulate so many mutations in its genome. </p>
<p>The origins of omicron are still poorly understood. One prevailing theory is that an immunocompromised person was infected with a coronavirus for an <a href="https://doi.org/10.1056/NEJMc2031364">extended period of time</a>, leading to <a href="https://doi.org/10.1016/j.chom.2022.01.005">accelerated viral evolution</a>. <a href="https://www.statnews.com/2021/12/02/some-experts-suggest-omicron-variant-may-have-evolved-in-an-animal-host/">Another theory</a> speculates that omicron could have evolved in another animal species and then reinfected humans. Alternatively, omicron could have evolved gradually in a location with poor <a href="https://theconversation.com/from-delta-to-omicron-heres-how-scientists-know-which-coronavirus-variants-are-circulating-in-the-us-173971">sequencing surveillance</a>. There is still much more that needs to be understood about the factors that led to the emergence of this highly mutated variant.</p>
<h2>Could omicron mutate to become more deadly?</h2>
<p>The variants that have risen to prominence have done so because they contain advantageous mutations for the coronavirus. We are essentially witnessing Darwinian evolution – survival of the fittest – in real time. Variants with beneficial mutations, such as those providing escape from antibodies or shorter incubation periods, are rapidly displacing their less fit predecessors. </p>
<p>The most important thing to remember about virus evolution is that natural selection favors variants that spread better than other variants. The great news is that more pathogenic – or dangerous – variants are less likely to spread well. This is because individuals who feel particularly sick tend to naturally self-isolate, reducing the virus’s chance to transmit. </p>
<p>Also good news is that, because infection with one variant <a href="https://doi.org/10.1101/2022.01.05.22268782">provides partial immunity to others</a>, omicron’s rapid spread has brought on delta’s swift decline. </p>
<p>At this point it is expected that all new variants that spread widely – so-called <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-classifications.html#anchor_1632154493691">variants of concern</a> – will continue to be highly transmissible. </p>
<h2>What about the buzz around ‘deltacron’ and ‘flurona’?</h2>
<p>In early January 2022, researchers in Cyprus reported cases of COVID-19 infections containing <a href="https://www.bloomberg.com/news/articles/2022-01-08/cyprus-finds-covid-19-infections-that-combine-delta-and-omicron">sequences of both omicron and delta</a>, dubbed “deltacron.” However, other scientists are speculating that this is nothing more than a <a href="https://www.independent.co.uk/news/science/covid-omicron-deltacron-variant-lab-b1992996.html">laboratory contaminant</a> – an omicron sample contaminated with delta. While more details are needed, as of now, there is not cause for alarm over this possible hybrid because it has not been commonly observed.</p>
<p>And in recent weeks <a href="https://www.washingtonpost.com/health/2022/01/05/flurona-coronavirus-flu-symptoms/">the term “flurona” has surfaced</a>, referring to an individual who is infected with both influenza virus and a coronavirus at the same time. While rare, such situations do happen, and it’s important that you reduce your risk by receiving both the influenza and COVID-19 vaccines. But it’s important to note that flurona is not a new combination of the flu and coronavirus genomes, making this term a bit of a misnomer.</p><img src="https://counter.theconversation.com/content/174703/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Sawyer is a co-founder of Darwin Biosciences. She receives funding from the National Institutes of Health and the Department of Defense.</span></em></p><p class="fine-print"><em><span>Cody Warren receives funding from the National Institutes of Health. </span></em></p><p class="fine-print"><em><span>Arturo Barbachano-Guerrero does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>People are buzzing with questions about the omicron variant and whether it could help usher in herd immunity. A team of virologists deciphers the latest findings.Sara Sawyer, Professor of Molecular, Cellular and Developmental Biology, University of Colorado BoulderArturo Barbachano-Guerrero, Postdoctoral Fellow in Virology, University of Colorado BoulderCody Warren, Postdoctoral Fellow in Virology and Immunology, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1735542021-12-15T19:49:31Z2021-12-15T19:49:31ZHow effective are vaccines against omicron? An epidemiologist answers 6 questions<figure><img src="https://images.theconversation.com/files/437635/original/file-20211214-15-12p1fq7.jpg?ixlib=rb-1.1.0&rect=134%2C0%2C5856%2C3880&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Understanding how much protection a vaccine offers is not as simple as it sounds.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/covid-19-vaccine-royalty-free-image/1287544065?adppopup=true">Andriy Onufriyenko/Moment via Getty Images</a></span></figcaption></figure><p><em>The pandemic has brought many tricky terms and ideas from epidemiology into everyone’s lives. Two particularly complicated concepts are vaccine <a href="https://theconversation.com/pfizer-vaccine-what-an-efficacy-rate-above-90-really-means-149849">efficacy and effectiveness</a>. These are not the same thing. And as time goes on and new variants like omicron emerge, they are changing, too. Melissa Hawkins is an <a href="https://www.american.edu/cas/faculty/mhawkins.cfm">epidemiologist and public health researcher</a> at American University. She explains the way researchers calculate how well a vaccine prevents disease, what influences these numbers and how omicron is changing things.</em></p>
<h2>1. What do vaccines do?</h2>
<p>A <a href="https://www.cdc.gov/vaccinesafety/ensuringsafety/history/index.html">vaccine</a> activates the <a href="https://theconversation.com/how-mrna-vaccines-from-pfizer-and-moderna-work-why-theyre-a-breakthrough-and-why-they-need-to-be-kept-so-cold-150238">immune system to produce antibodies</a> that remain in your body to fight against exposure to a virus in the future. All three vaccines currently approved for use in the U.S. – the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines – showed <a href="https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html">impressive success in clinical trials</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A medical professional getting a shot." src="https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437637/original/file-20211214-19-kx4h5b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Clinical trials are used to calculate the efficacy of a vaccine but don’t necessarily represent real-world conditions.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakGeorgiaVaccineTrial/47e7e14cbd864228b79581d3e5bd8c23/photo?Query=vaccine%20trial&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=605&currentItemNo=5">AP Photo/Ben Gray</a></span>
</figcaption>
</figure>
<h2>2. What is the difference between vaccine efficacy and effectiveness?</h2>
<p>All new vaccines must undergo clinical trials in which researchers test the vaccines on thousands of people to examine how well they work and whether they are safe. </p>
<p><a href="https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html">Efficacy</a> is the measure of <a href="https://theconversation.com/pfizer-vaccine-what-an-efficacy-rate-above-90-really-means-149849">how well a vaccine works</a> in clinical trials. Researchers design the trials to include two groups of people: those who receive the vaccine and those who receive a placebo. They calculate the vaccine’s efficacy by comparing how many cases of the illness occur in each group, vaccinated versus placebo.</p>
<p><a href="https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html">Effectiveness</a>, on the other hand, describes how well a vaccine performs in the real world. It is calculated the same way, by comparing illness among vaccinated and unvaccinated people.</p>
<p>Efficacy and effectiveness are usually close to each other but won’t necessarily be the same. How the vaccines work will vary a bit from the trial results once millions of people are getting vaccinated.</p>
<p>Many factors influence how a vaccine performs in the real world. New variants like delta and omicron may change things. The number and age of people enrolled in the trials matter. And the health of those receiving the vaccine is also important.</p>
<p><a href="https://doi.org/10.1001/jamapsychiatry.2021.2497">Vaccine uptake</a> – the proportion of a population that gets vaccinated – can also influence vaccine effectiveness. When a large enough proportion of the population is vaccinated, herd immunity begins to come into play. Vaccines with <a href="https://www.cdc.gov/flu/vaccines-work/effectivenessqa.htm">moderate or even low efficacy can work very well</a> at a population level. Likewise, vaccines with high efficacy in clinical trials, like coronavirus vaccines, may have <a href="https://www.nature.com/articles/d41586-021-00728-2">lower effectiveness</a> and a small impact if there isn’t high vaccine uptake in the population.</p>
<p>The distinction between efficacy and effectiveness is important, because one describes the risk reduction achieved by the vaccines under trial conditions and the other describes how this may vary in populations with different exposures and transmission levels. Researchers can calculate both, but they can’t design a study that will measure both simultaneously. </p>
<h2>3. How do you calculate efficacy and effectiveness?</h2>
<p>Both <a href="https://pubmed.ncbi.nlm.nih.gov/33301246/">Pfizer</a> and <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm695152e1.htm?s_cid=mm695152e1_w">Moderna</a> reported that their vaccines demonstrated more than 90% efficacy in preventing symptomatic COVID-19 infection. Stated another way, among those individuals who received the vaccine in the clinical trials, the risk of getting COVID-19 was reduced by 90% compared with those who did not receive the vaccine. </p>
<p>Imagine conducting a vaccine trial. You randomize 1,000 people to receive the vaccine in one group. You randomize another 1,000 to be given a placebo in the other group. Say 2.5% of people in the vaccinated group get COVID-19 compared with 50% in the unvaccinated group. That means the vaccine has 95% efficacy. We determine that because (50% – 2.5%)/50% = .95. So 95% indicates the reduction in the proportion of disease among the vaccinated group. However, a vaccine with 95% efficacy does not mean 5% of vaccinated people will get COVID-19. It’s even better news: Your risk of illness is reduced by 95%.</p>
<p>Vaccine effectiveness is calculated the exact same way but is determined through <a href="https://dx.doi.org/10.17269%2Fs41997-021-00554-z">observational studies</a>. Early on, vaccines were well over <a href="https://www.statnews.com/2021/03/29/real-world-study-by-cdc-shows-pfizer-and-moderna-vaccines-were-90-effective/">90% effective</a> at preventing severe illness in the real world. But, by their very nature, <a href="https://doi.org/10.1038/d41586-021-03619-8">viruses change</a>, and this can change effectiveness. For example, a study found that by August 2021, when delta was surging, the Pfizer vaccine was <a href="http://dx.doi.org/10.15585/mmwr.mm7034e3">53% effective at preventing severe illness in nursing home residents</a> who had been vaccinated in early 2021. Age, health issues, waning immunity and the new strain all lowered effectiveness in this case.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A model of the coronavirus." src="https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437638/original/file-20211214-23-1e9wqqp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New variants of the coronavirus are all slightly different from the original strain that vaccines were based on, so immunity to variants may be different.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Coronavirus._SARS-CoV-2.png#/media/File:Coronavirus._SARS-CoV-2.png">Alexey Solodovnikov, Valeria Arkhipova/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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</figure>
<h2>4. What about the omicron variant?</h2>
<p>The preliminary data about omicron and vaccines is <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-covid-19-vaccine-partially-protective-against-omicron-bloomberg-news-2021-12-07/">coming in quickly</a> and is revealing lower vaccine effectiveness. Best estimates suggest vaccines are around <a href="https://www.medpagetoday.com/special-reports/exclusives/96172">30%-40% effective at preventing infections</a> and <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-vaccine-protecting-against-hospitalisation-during-omicron-wave-study-2021-12-14/">70% effective at preventing severe disease</a>.</p>
<p>A <a href="https://www.medrxiv.org/content/10.1101/2021.12.07.212%2067432v1">preprint study</a> – one not formally reviewed by other scientists yet – that was conducted in Germany found that antibodies in blood collected from people fully vaccinated with Moderna and Pfizer showed <a href="https://doi.org/10.1038/d41586-021-03672-3">reduced efficacy in neutralizing the omicron variant</a>. Other small preprint <a href="https://doi.org/10.1101/2021.12.08.21267417">studies in South Africa</a> and <a href="https://www.medrxiv.org/content/10.1101/2021.12.10.21267534v1.full">England</a> showed a significant decrease in how well antibodies target the omicron variant. More <a href="https://www.npr.org/sections/goatsandsoda/2021/12/14/1063947940/vaccine-protection-vs-omicron-infection-may-drop-to-30-but-does-cut-severe-disea">breakthough infections are expected</a>, with decreased immune system ability to recognize omicron compared with other variants. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sign outside of a pharmacy saying vaccines are available for walk-in appointments." src="https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437636/original/file-20211214-15-862uwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most people in the U.S. are now eligible to get a booster coronavirus vaccine which could help protect against the omicron variant.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakIllinois/07e30f89e82f47a8a6a575d3c2e8080b/photo?Query=booster%20vaccine%20sign&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=50&currentItemNo=4">AP Photo/Nam Y. Huh</a></span>
</figcaption>
</figure>
<h2>5. Do boosters boost immunity against omicron?</h2>
<p>Initial data reinforces that <a href="https://theconversation.com/should-i-get-my-covid-vaccine-booster-yes-it-increases-protection-against-covid-including-omicron-172965">a third dose would help boost</a> immune response and protection against omicron, with estimates of <a href="https://www.cnbc.com/2021/12/10/boosters-give-70percent-75percent-protection-against-mild-disease-from-omicron-uk-health-security-agency-says.html">70%-75% effectiveness</a>. </p>
<p><a href="https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-provide-update-omicron-variant">Pfizer has reported</a> that people who have received two doses of its vaccine are susceptible to infection from omicron, but that a <a href="https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-provide-update-omicron-variant">third shot improves antibody activity against the virus</a>. This was based on lab experiments using the blood of people who have received the vaccine. </p>
<p>Booster doses can increase the amount of antibodies and the ability of a person’s immune system to protect against omicron. However, unlike the U.S., much of the <a href="https://ourworldindata.org/covid-vaccinations">world does not have access</a> to booster doses.</p>
<h2>6. What does this all mean?</h2>
<p>Despite the lowered effectiveness of vaccines against omicron, it is clear that vaccines do work and are among the <a href="https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6019a5.htm">greatest public health achievements</a>. Vaccines have varying levels of effectiveness and are still useful. The flu vaccine is usually <a href="https://www.cdc.gov/flu/vaccines-work/vaccineeffect.htm">40%-60% effective</a> and prevents illness in millions of people and hospitalizations in more than 100,000 people in the U.S. <a href="https://www.cdc.gov/flu/about/burden-averted/2019-2020.htm">annually</a>.</p>
<p>Finally, vaccines protect not only those who are vaccinated, but those who can’t get vaccinated as well. Vaccinated people are <a href="https://theconversation.com/no-vaccinated-people-are-not-just-as-infectious-as-unvaccinated-people-if-they-get-covid-171302">less likely to spread</a> COVID-19, which reduces new infections and offers protection to society overall.</p>
<p>[<em><a href="https://memberservices.theconversation.com/newsletters?nl=science&source=inline-science-corona-important">Get The Conversation’s most important coronavirus headlines, weekly in a science newsletter</a></em>]</p><img src="https://counter.theconversation.com/content/173554/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Melissa Hawkins receives funding from USDA/NIFA. </span></em></p>For a number of reasons, as time goes on vaccines become less effective. So how do researchers calculate how well vaccines are working?Melissa Hawkins, Professor of Public Health, American UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1730022021-12-03T14:07:37Z2021-12-03T14:07:37ZOmicron: Britain plans to vaccinate 25 million in two months – but can it be done?<p>What impact the new omicron variant will have is still unknown. But with early data suggesting it could be the <a href="https://theconversation.com/omicron-why-the-who-designated-it-a-variant-of-concern-172727">most transmissible</a> form of the virus yet – and that it could be <a href="https://www.ft.com/content/2e272227-26b8-4dd7-9380-0c95bd8952ed">less susceptible</a> to existing antibodies – it <a href="https://news.sky.com/story/covid-19-emerging-picture-from-south-africa-suggests-omicron-variant-could-be-real-cause-for-concern-12484064">shouldn’t be taken lightly</a>.</p>
<p>The World Health Organization <a href="https://www.who.int/news/item/28-11-2021-update-on-omicron">has advised</a> countries to take precautions to limit its impact, such as upping the wearing of masks, sanitising of hands and surfaces, social distancing and ventilation of shared spaces. </p>
<p>The UK has gone one step further: it’s also expanding its <a href="https://www.gov.uk/government/news/all-adults-to-be-offered-covid-19-boosters-by-end-of-january">COVID vaccine booster programme</a>. COVID boosters have been available for some time for older and more vulnerable people, and there’s <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02717-3/fulltext">evidence</a> that they <a href="https://www.bmj.com/content/374/bmj.n2297">reduce infections and severe disease</a> in those groups by topping up <a href="https://www.nature.com/articles/d41586-021-02532-4">waning immunity</a>. </p>
<p>Given concern about the increased transmissibility of omicron, its potential ability to get around existing antibodies, and that we don’t know if it causes more or less severe disease, maximising the population’s immunity is prudent. Everything we’ve learned so far suggests that recently administered vaccines are our best line of defence.</p>
<p>So here’s what’s planned. Third doses will now be available to adults <a href="https://www.theguardian.com/world/2021/nov/29/covid-booster-jabs-to-be-offered-to-all-uk-adults-after-three-month-gap">three months</a> after their second vaccination. Before this the gap was six months. This means all people over 18 will be offered a third dose by the end of January 2022. Prioritisation will start with those oldest and descend in bands of five years.</p>
<p>At the same time, second doses will be offered to 12 to 15-year-olds and fourth doses to people who are immunosuppressed. This adds up to giving <a href="https://news.sky.com/story/covid-19-booster-jabs-for-all-adults-as-vaccine-advisers-announce-rollout-expansion-to-combat-omicron-variant-12482072">25 million people</a> a booster dose in under two months. Combined with the fact that first and second doses are still being rolled out to some people, the government will need to hit a target of delivering <a href="https://www.theguardian.com/world/2021/nov/29/covid-uk-aims-500000-jabs-a-day-in-bid-to-outpace-omicron-variant">500,000 vaccinations</a> a day. Achieving this will require immense logistical coordination and resource management. </p>
<h2>Can it be done?</h2>
<p>There have been concerns about the speed at which the booster programme has moved so far. Patients have been confused about their <a href="https://www.bmj.com/content/375/bmj.n2702">eligibility for a third dose</a> and concerned about the apparent lack of urgency compared to the initial vaccination campaign. Some have <a href="https://www.theguardian.com/society/2021/dec/01/sajid-javid-covid-booster-jabs-nhs-national-mission-gps-appointments-vaccination">struggled to get an appointment</a> despite being eligible and have not been contacted to choose a booking via the NHS website. </p>
<p>Current booster delivery is 350,000 doses a day, and since boosters started being delivered two and a half months ago, 19 million people have received one. Given the challenge now is to deliver more – 25 million – in just under two months, the government needs to work harder to get the booster campaign fully firing. </p>
<p>The government has a plan for meeting this challenge. It’s promised that many temporary vaccination points will be created – up to <a href="https://www.theguardian.com/world/2021/dec/01/the-new-covid-vaccine-booster-drive-questions-and-answers">3,000 has been quoted</a> – which will be staffed with existing NHS staff and 10,000 newly appointed vaccinators and volunteers.</p>
<p>Vaccination sites used in the first rollout will be re-opened, the idea being that these familiar sites may ease any hesitancy and access issues. There will also be increased use of community pharmacies.</p>
<p>NHS organisations are already delivering booster doses, and will now work at <a href="https://www.yorkshirepost.co.uk/news/politics/hundreds-of-coronavirus-booster-vaccines-delivered-by-candlelight-in-north-yorkshire-after-storm-arwen-says-nhs-boss-3477348">“breakneck speed”</a> to accelerate delivery, with <a href="https://www.gov.uk/government/speeches/pm-opening-statement-at-covid-19-press-conference-30-november-2021">extra hospital vaccination hubs</a> being opened. However, with the NHS under stress – with intense winter pressures and pent-up healthcare demand from earlier in the pandemic – there are <a href="https://www.bbc.co.uk/news/uk-wales-59482080">concerns</a> that it doesn’t have the capacity to up its vaccine delivery.</p>
<p>Noting this, the government has agreed to <a href="https://inews.co.uk/news/covid-booster-jabs-gps-paid-per-vaccine-administered-rollout-ramped-up-1328159">increase the amount of money</a> it gives to the health service for each dose delivered – with even greater increases for vaccines delivered on Sundays and, where required, in patients’ homes. These payments will allow NHS professionals to prioritise administering vaccines and bring in additional staff to backfill existing work. A <a href="https://www.bbc.co.uk/news/uk-wales-59482080">“Jabs Army”</a> will also be in force, with soldiers and firefighters helping to immunise people too.</p>
<p>Boosting the population should also, hopefully, reduce the number of COVID patients needing care over the winter months, and so relieve pressure on the NHS in the longer term. </p>
<p>Finally, supplies of the two vaccines to be used as boosters – <a href="https://inews.co.uk/news/health/why-astrazeneca-not-used-booster-jabs-covid-vaccine-pfizer-moderna-explained-1330966">Pfizer and Moderna</a> – have been assured, with <a href="https://news.sky.com/story/covid-19-uk-government-secure-114-million-more-vaccines-doses-for-the-next-two-years-as-cases-of-the-new-omicron-variant-rise-12484008">114 million more doses</a> ordered for the next two years.</p>
<p>The key ingredients for a successful booster programme have thus been promised – vaccine stock, vaccination sites and staff resources. If they can be made available in a timely fashion, then replicating the vaccination drive of the first half of 2021 is possible – as is meeting the government’s January target. Encouragingly, vaccination rates were <a href="https://coronavirus.data.gov.uk/details/vaccinations">already improving</a> before these changes. </p>
<p>Past experience shows that the vaccination programme can adjust rapidly. The experience held and training provided to staff involved in the initial COVID vaccine rollout will be invaluable in setting up and running new vaccination centres.</p>
<p>The best way we can help with the vaccine rollout is to book our booster appointments when asked to do so. Despite not knowing what impact omicron will have, we can be sure that collectively taking our boosters will give us the best chance of minimising its effects.</p><img src="https://counter.theconversation.com/content/173002/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Half a million British people need to be given a COVID vaccine each day between now and the end of January 2022.Liz Breen, Director of the Digital Health Enterprise Zone (DHEZ), University of Bradford, Reader in Health Service Operations, University of BradfordAnthony R Cox, Reader in Clinical Pharmacy and Drug Safety, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1711412021-11-05T15:52:21Z2021-11-05T15:52:21ZTop scientist: why South Africa shouldn’t be giving 12-17 year olds COVID shots – now<figure><img src="https://images.theconversation.com/files/430465/original/file-20211105-29-11sshib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People queuing to get vaccinated. Instead of vaccinating 12-17 year olds, government should focus on giving boosters to people who need it.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>South Africa is one of the leading countries in Africa in terms of COVID vaccine rollout, along with <a href="https://www.afro.who.int/news/fifteen-african-countries-hit-10-covid-19-vaccination-goal">Mauritius, Tunisia and Morocco</a>. It has, however, had it’s fair share of challenges. Shabir Madhi has been a key player in shaping the country’s response. Ina Skosana and Ozayr Patel asked him for an assessment of <a href="https://www.nicd.ac.za/covid-19-unpacking-south-africas-plan-to-vaccinate-adolescents/">plans to vaccinate adolescents</a>, and next steps.</em></p>
<p><audio preload="metadata" controls="controls" data-duration="1520" data-image="" data-title="Pasha 132: Why South Africa should not vaccinate 12 to 17-year-olds yet" data-size="24390470" data-source="The Conversation Africa" data-source-url="" data-license="CC BY-NC-ND" data-license-url="http://creativecommons.org/licenses/by-nc-nd/4.0/">
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Pasha 132: Why South Africa should not vaccinate 12 to 17-year-olds yet.
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<h2>Should South Africa be vaccinating adolescents?</h2>
<p>I don’t believe this is the most efficient use of the vaccines. In a country like South Africa, we’d be much better off offering a third dose of the Pfizer/BioNTech vaccine to the 65% of adults above the age of 65 who have been vaccinated, and intensifying efforts at vaccinating the elderly and high risk groups who have not yet received even a single dose. </p>
<p>We shouldn’t be using these vaccines to give to children between 12 to 17 years a single dose.</p>
<p>Young children rarely get severe disease from COVID-19. Vaccinating children with a single dose of the Pfizer vaccine is unlikely to provide much value to the child in terms of individual protection, unless they have underlying medical conditions pre-disposing them to severe COVID-19. If this is the case they should receive the full two dose schedule. A single dose also doesn’t work too well in reducing the ability of a person to <a href="https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/covid-19-vaccine-what-you-need-to-know">transmit the virus</a>. </p>
<p>This is the main reason <a href="https://www.nicd.ac.za/covid-19-unpacking-south-africas-plan-to-vaccinate-adolescents/">being given</a> for vaccinating 12 to 17 year olds. </p>
<p>South Africa might be banking on the fact that a large percentage of the population – estimates are between <a href="https://www.news24.com/fin24/companies/health/80-of-south-africans-may-have-had-covid-discovery-says-20210818">70% to 80%</a> – might have been infected already. In that context, a single dose of vaccine is probably all you require to protect against severe COVID-19. </p>
<p>This hybrid immunity, where you start off with your immune system being primed by natural infection followed by a vaccine, induces quite potent immunity. Consequently, people that have passed infection probably only require a single dose of any vaccine. That’s the only way South Africa can really justify using a single dose of vaccine in the 12 to 17 year old age group. Needless to say, waiting to get infected and risking developing long-COVID, being hospitalised for COVID-19 or dying from COVID-19 is not really a bright idea. </p>
<p>The liberal rollout of COVID-19 vaccines in South Africa to low risk groups, such as young children, appears to be more about chasing after numbers rather than deriving the maximal protection against severe disease and deaths. </p>
<p>I’m not saying that you shouldn’t vaccinate children. There’s a time and place. But that time and place is not right now in South Africa, or globally in the context of the tragic inequity of vaccine access. </p>
<p>Starting to vaccinate children against COVID-19 (and use of booster doses in healthy adults) is more than just a country specific decision. Most countries on the continent have less than 5% of the <a href="https://www.one.org/africa/issues/covid-19-tracker/explore-vaccines/">adult population vaccinated</a>, and in fact, less than 10% of people above the age of 60 <a href="https://ourworldindata.org/covid-vaccinations">are vaccinated</a>. </p>
<p>This is being perpetuated by countries with access to vaccines using them liberally.</p>
<h2>Would you recommend a booster for the general population?</h2>
<p>Absolutely. For certain groups of adults. </p>
<p>We now understand that the first two doses of vaccine provide good protection against severe disease in people above the <a href="https://www.ncoa.org/article/covid-vaccines-what-seniors-need-to-know">age of 65</a> and those with other underlying medical conditions. However, it is also apparent that people older than 65 or with underlying immunosupressive medical conditions require a third dose of the mRNA vaccines, such as by Pfizer/Biontech. This is required to boost their immune response and enhance their protection even against severe COVID-19.</p>
<p>The primary goal of vaccination therefore needs to be on reducing severe disease and death. This requires targeted strategies on who to prioritise.</p>
<p>Evidence <a href="https://www.yalemedicine.org/news/johnson-and-johnson-covid-booster">from the US</a> is that a two dose schedule of the Johnson & Johnson vaccine is superior in protecting against hospitalisation than a single dose. And if you want durability of protection, you need to boost, which can be done with another dose of Johnson & Johnson. </p>
<p>My own preference is to boost with one of the messenger RNA vaccines. In South Africa this is the Pfizer vaccine. The evidence <a href="https://www.npr.org/sections/health-shots/2021/10/13/1045485935/study-of-covid-vaccine-boosters-suggests-moderna-or-pfizer-works-best">is clear</a> that the type of immune responses from this approach is superior to two doses of the J&J vaccine and possibly even two doses of the Pfizer vaccine. </p>
<h2>Is vaccine coverage high enough to justify boosters?</h2>
<p>Absolutely. If we can justify providing vaccines to the 12 to 17 year old age group, it means we’ve got vaccines that we don’t know what to do with.</p>
<p>In my view it would be much better offering these doses to boost adults above the age of 55. In particular, people older than 65 do require an additional dose of the Pfizer vaccine after they’ve had two shots. The same thing goes for other risk groups such as people with kidney transplants, or people with cancer and on chemotherapy, people with any other sort of underlying immunosuppressive condition. </p>
<p>South Africa is, once again, going against the World Health Organisation which <a href="https://www.who.int/emergencies/diseases/novel-coronavirus-2019/media-resources/science-in-5/episode-53---covid-19-booster-shots">is recommendating</a> booster doses of such high risk groups, and instead vaccinating young children. </p>
<h2>Is South Africa in a stable position vis-a-vis another surge?</h2>
<p>The main thing that’s going to determine how well the country manages another resurgence is the percentage of people above the age of 50 who have been vaccinated. We need to get 85% to 90% of this age group vaccinated and 80% of those with underlying medical conditions. </p>
<p>If we don’t reach those marks, when we do have a resurgence – and we will have a resurgence in the next two to three months – it will end up with hospitals coming under pressure once again. </p>
<p>What’s in South Africa’s favour is the high percentage of the population that’s been infected with the virus. Natural infection does seem to confer protection against <a href="https://www.nature.com/articles/d41586-021-02795-x">severe disease</a>. </p>
<p>So this combination of natural immunity – probably 75% to 80% of the population has now have developed some level of <a href="https://www.news24.com/fin24/companies/health/80-of-south-africans-may-have-had-covid-discovery-says-20210818">natural immunity</a> – coupled with vaccine induced immunity and a hybrid of the two probably puts South Africa in a relatively stable position in relation to severe cases likely to be lower with a future resurgence than experienced in the past. This could, however, change if there are new major immune-evasive mutations in the virus. </p>
<h2>What’s been learnt from the vaccine roll-out in South Africa?</h2>
<p>We’ve learned that rolling out a vaccine is as complex as securing supplies. And we’ve missed some targets.</p>
<p>For example, we were meant to have vaccinated the majority of people above the age of 60 by July this year. Currently we’re sitting at around about 62% to 63% of people above <a href="https://sacoronavirus.co.za/latest-vaccine-statistics/">the age of 60</a>. In the 50 to 59 year age group we are looking at <a href="https://sacoronavirus.co.za/latest-vaccine-statistics/">just over 50%</a>. </p>
<p>The reasons are multiple. But part of it speaks to the issue of planning and rollout, not just in South Africa, but in many countries. People don’t appreciate what it entails, starting from community engagement, adequate communication around what the vaccines are about, what the purpose of the vaccine programme is, and then finally being able to implement. </p>
<p>The other challenge was that the initial planning for the rollout was top down. The expectation was that people were going to rush forward to register on the <a href="https://vaccine.enroll.health.gov.za/#/">electronic vaccine data system</a> without really understanding how adaptable it was for South Africa. The system was inaccessible to most people.</p>
<p>There was a quick escalation in coverage once walk ins were set up for targeted age groups. Also, the use of pop up facilities is beginning to play a big part in increasing <a href="https://www.africanews.com/2021/08/22/south-africa-pop-up-vaccination-centres-boost-number-of-jabs//">vaccine coverage rates</a>.</p>
<p>This also speaks to the issue of community sensitisation and engagement of community structures. Unfortunately resources set aside for this purpose were siphoned off by <a href="https://www.dailymaverick.co.za/article/2021-10-19-digital-vibes-scandal-the-story-behind-the-story/">corruption</a>. </p>
<p>Also, South Africa hasn’t had enough champions across the spectrum of society. In other countries support this has been a major contributor to success.</p>
<p>On the plus side, South Africa secured adequate supplies of vaccine. That in itself was quite an achievement, considering the poor planning until Government came under pressure early in January 2021. The challenge now is being able to use the doses wisely before they expire.</p><img src="https://counter.theconversation.com/content/171141/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shabir A. Madhi receives funding from BMGF, SAMRC and Novavax related to COVID-19 studies. All funding goes to his institution.</span></em></p>The focus of the government seems to be about how many people can get vaccinated rather than ensuring the greatest protection against severe disease and deaths.Shabir A. Madhi, Dean Faculty of Health Sciences and Professor of Vaccinology at University of the Witwatersrand; and Director of the SAMRC Vaccines and Infectious Diseases Analytics Research Unit, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1703682021-10-27T02:03:48Z2021-10-27T02:03:48ZAustralians will soon receive COVID booster vaccines. Why do we need them, and how effective are they?<p>Australia’s drug regulator, the Therapeutic Goods Administration (TGA), today <a href="https://www.tga.gov.au/media-release/tga-approves-booster-doses-pfizer-covid-19-vaccine-comirnaty">provisionally approved the Pfizer COVID vaccine to be used as a booster</a> for anyone over the age of 18.</p>
<p>The TGA said people can take the third dose from six months after their second dose.</p>
<p>People can take Pfizer as a third dose regardless of which two shots they got first.</p>
<p>Moderna’s vaccine is yet to be approved as a booster, while the federal government <a href="https://www.health.gov.au/ministers/the-hon-greg-hunt-mp/media/minister-hunts-press-conference-in-canberra-on-20-october-2021-on-the-vaccination-rollout-vaccine-booster-update-stem-cell-mission-grants-booster-program-and-net-zero-emissions-policy">does not expect AstraZeneca’s vaccine to be used as a booster</a>.</p>
<p>Health Minister Greg Hunt said he expects <a href="https://www.abc.net.au/news/2021-10-27/tga-approves-covid-vaccine-booster-shots-for-over-18-year-olds/100571442">the booster program to start from November 8</a>. However, the federal government is awaiting further advice from the Australian Technical Advisory Group on Immunisation (ATAGI) about who should receive it and when.</p>
<p>Given our approved vaccines were originally marketed as two-dose jabs, why are we now looking at an extra dose?</p>
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<h2>Why another jab?</h2>
<p>Scientists have often said we may <a href="https://theconversation.com/why-do-we-need-booster-shots-and-could-we-mix-and-match-different-covid-vaccines-155951">need another jab</a> in the future to have better long-term protection against COVID. This is because of concerns about the possibility the immunity will decrease over time. </p>
<p>Initially it was hard to predict when this might happen. But it’s clear now the need and timing for an extra vaccine dose depends on what group of people you’re talking about.</p>
<p>For those living with cancer or other diseases affecting the immune system, current COVID vaccines often <a href="https://www.nature.com/articles/s41591-021-01542-z">fail to generate a strong level of immunity</a>. Getting a third dose seems to help, leading the <a href="https://www.thelancet.com/journals/lanrhe/article/PIIS2665-9913(21)00313-1/fulltext">United States and United Kingdom</a> to recommend additional jabs for people who are immunocompromised. </p>
<p>Earlier in October, boosters for people who are severely immunocompromised became available in <a href="https://www.health.gov.au/resources/publications/atagi-recommendations-on-the-use-of-a-third-primary-dose-of-covid-19-vaccine-in-individuals-who-are-severely-immunocompromised">Australia</a>. These are available <a href="https://www.smh.com.au/politics/federal/tga-approves-pfizer-booster-shots-for-all-adults-20211027-p593hp.html">28 days after the second dose</a>.</p>
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<a href="https://theconversation.com/why-is-a-third-covid-19-vaccine-dose-important-for-people-who-are-immunocompromised-166569">Why is a third COVID-19 vaccine dose important for people who are immunocompromised?</a>
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<p>Among those who do have a strong response to a two-dose vaccine, their level of protection against infection or serious disease is being tracked over time.</p>
<p>Earlier this year, Israel reported increasing rates of infection in fully vaccinated people aged 60 years and older. This led the government to <a href="https://www.reuters.com/world/middle-east/israel-offer-third-shot-pfizer-vaccine-people-over-60-israeli-news-reports-2021-07-29/">provide third doses</a> for this age group.</p>
<p>In the short-term, the strategy appears to have worked, with <a href="https://www.nejm.org/doi/full/10.1056/NEJMoa2114255">infections dropping ten-fold</a> at least two weeks after the boost.</p>
<h2>What is ‘waning immunity’?</h2>
<p>We’ve heard a lot about “waning immunity”, but this may actually be referring to more than one topic.</p>
<p>Across a population, we can track how well vaccines are performing at preventing people from getting infected, getting sick, or needing to go to the hospital. </p>
<p>There is evidence of gradual <a href="https://www.nature.com/articles/d41586-021-02532-4">decreasing vaccine effectiveness</a> over time. </p>
<p>However, the ability of vaccination to <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02183-8/fulltext">prevent hospitalisation from COVID remains very high</a> even after six months.</p>
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<p>At an individual level, scientists can also study the waning of immune responses over time.</p>
<p>There are two key parts to this immunity: the antibodies that can bind to the virus and stop infection completely, and the cells that remember the virus for (hopefully) years to come, ready to be reactivated if the virus gets in.</p>
<p>After a few months, the levels of these antibodies have <a href="https://www.nejm.org/doi/full/10.1056/NEJMoa2114583">dropped somewhat</a> among those who receive two doses, likely explaining why vaccine effectiveness declines and breakthrough infections in fully vaccinated people occur. </p>
<p>But if our immunity drops, why are people still protected from hospitalisation and severe disease?</p>
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<p>That’s where our immune memory comes in. If you do get infected after being vaccinated, your white blood cells will quickly jump into action, producing lots of antibodies and getting ready to kill the virus.</p>
<p>Although longer-term immunity from vaccination dramatically reduces the need for hospitalisation, breakthrough infections following the waning of immunity <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7038e3.htm">do result in further spread of the virus</a>, complicating efforts to control the epidemic.</p>
<p>So, after six months, the vaccines may be less likely to stop us from becoming infected at all, but they’re still extremely important for preventing hospitalisation and death.</p>
<p>Therefore, administering boosters will likely reduce infection and transmission, but the effect of boosters to prevent serious disease and death is more modest, at least in those under 60.</p>
<h2>Are boosters effective?</h2>
<p><a href="https://www.nature.com/articles/s41591-021-01527-y">Early reports</a> have shown strong immune responses to the third dose, and similar side effects to the first shots (mostly pain and fatigue).</p>
<p>Vaccinating people who previously received AstraZeneca with mRNA vaccines can produce <a href="https://www.nature.com/articles/s41591-021-01463-x">particularly strong antibody responses</a>.</p>
<p>This is important in Australia, as most vulnerable older people received the comparatively less potent AstraZeneca vaccine, and using a potent mRNA booster vaccine is wise.</p>
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<h2>3-dose vaccine, or booster dose?</h2>
<p>Most discussion of additional doses uses the terms “third dose” and “booster dose” interchangeably. But there’s a key distinction.</p>
<p>Many vaccines for other diseases are given as <a href="https://www.health.gov.au/health-topics/immunisation/immunisation-throughout-life/national-immunisation-program-schedule">three-dose vaccines</a>, including the Hepatitis B and Human Papillomavirus (HPV) vaccines. In these cases, you’re considered fully vaccinated after having three doses, and in some cases, are expected to have life-long immunity.</p>
<p>This is different from situations in which people might need intermittent booster vaccines to maintain their immunity, such as the annual flu vaccine. </p>
<p>For COVID, a third dose vaccine isn’t likely to provide life-long immunity against any infection, and further doses may be needed.</p>
<p>The third dose of Pfizer will be the same formulation that’s currently being given across Australia. In the US, Moderna is planning to administer <a href="https://apnews.com/article/coronavirus-pandemic-vaccine-moderna-booster-shot-fda-2de19cdff021ad11b95c6b67fd5d8617">a half-dose</a> as the third shot. </p>
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Read more:
<a href="https://theconversation.com/can-i-get-astrazeneca-now-and-pfizer-later-why-mixing-and-matching-covid-vaccines-could-help-solve-many-rollout-problems-161404">Can I get AstraZeneca now and Pfizer later? Why mixing and matching COVID vaccines could help solve many rollout problems</a>
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<h2>When should boosters be given?</h2>
<p>The best timing of third doses for widespread use isn’t yet clear, and there are two conflicting considerations.</p>
<p>On the one hand, earlier administration will provide more immediate protection from breakthrough infections and virus spread.</p>
<p>However, a longer gap between vaccine doses <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00432-3/fulltext">generally results in higher and more durable immunity</a>.</p>
<p>The best timing of booster vaccines requires careful follow-up in trials.</p>
<h2>Are boosters ethical?</h2>
<p>There’s a question about whether wealthy countries should be embarking on third-dose rollouts given global vaccine supply is limited.</p>
<p>Many developing countries have vaccinated very small proportions of their populations. They remain vulnerable to widespread outbreaks and the overwhelming of already fragile health-care systems.</p>
<p>Also, large numbers of infections across the world can drive additional variants and economic and political instability.</p>
<p>There’s a moral and political imperative for wealthy countries to <a href="https://www.who.int/initiatives/act-accelerator/covax">donate vaccines</a> to initiatives such as the World Health Organization’s COVAX program.</p>
<p>In this context, the decision to <a href="https://www.abc.net.au/news/2021-10-14/opposition-aid-groups-urge-government-extend-csl-astra-zeneca/100539494">shut down local manufacturing of the AstraZeneca vaccine</a> in Australia from early next year is disappointing. Australia had been exporting many of these doses to its Pacific neighbours.</p>
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Read more:
<a href="https://theconversation.com/are-covid-19-boosters-ethical-with-half-the-world-waiting-for-a-first-shot-a-bioethicist-weighs-in-167606">Are COVID-19 boosters ethical, with half the world waiting for a first shot? A bioethicist weighs in</a>
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<img src="https://counter.theconversation.com/content/170368/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Juno receives funding from the National Health and Medical Research Council and the Medical Research Future Fund.</span></em></p><p class="fine-print"><em><span>Stephen Kent receives funding from the Australian National Health and Medical Research Council and the Medical Research Future Fund.</span></em></p>Protection from infection wanes over time. So boosters will offer extra protection and hopefully reduce the spread of the virus even further.Jennifer Juno, Senior research fellow, The Peter Doherty Institute for Infection and ImmunityStephen Kent, Professor and Laboratory Head, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1692322021-10-13T12:17:48Z2021-10-13T12:17:48ZVaccination against COVID-19 supports a healthy pregnancy by protecting both mother and child – an immunologist explains the maternal immune response<figure><img src="https://images.theconversation.com/files/426045/original/file-20211012-21-1t9uohx.jpg?ixlib=rb-1.1.0&rect=19%2C0%2C2121%2C1400&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pregnancy poses significant risks for severe illness or death from COVID-19, for both mother and baby. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-nurse-giving-vaccine-injection-to-pregnant-royalty-free-image/1328370968?adppopup=true">ArtMarie/E+ via Getty Images</a></span></figcaption></figure><p>The CDC issued an <a href="https://www.cdc.gov/media/releases/2021/s0929-pregnancy-health-advisory.html">urgent health advisory</a> for those currently pregnant, planning a pregnancy or breastfeeding on Sept. 29, 2021. The statement reiterated the importance of vaccination in preventing severe illness and death resulting from COVID-19. It also highlighted the wide gap in vaccination rates with pregnant people who are <a href="https://www.cdc.gov/media/releases/2021/s0929-pregnancy-health-advisory.html">less than half</a> as likely to have been vaccinated than a member of the <a href="https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-total-admin-rate-total">general public</a>. </p>
<p>The CDC advisory also brought attention to the widening racial gaps in vaccination during pregnancy, with <a href="https://www.cdc.gov/media/releases/2021/s0929-pregnancy-health-advisory.html">less than 16%</a> of Black pregnant females reporting having been vaccinated.</p>
<p>As <a href="https://scholar.google.com/citations?user=-oDHlFYAAAAJ&hl=en">an immunologist</a> who has been studying <a href="https://doi.org/10.1038/s41590-020-00814-z">immune responses to COVID-19</a> since the beginning of the pandemic, I know the reason for the agency’s urgency is clear. Pregnancy is a significant risk factor for serious illness and death from COVID-19 – both for the mother and the child. Detailed research into pregnancy during the pandemic has shown that mothers who contract COVID-19 are five times more likely to be admitted to an ICU and 22 times more likely to die <a href="https://doi.org/10.1001/jamapediatrics.2021.1050">than their noninfected counterparts</a>. </p>
<p>The same study found that mothers infected with COVID-19 during pregnancy are twice as likely to require ICU care for their newborns, or to lose their children shortly after birth.</p>
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<img alt="A pregnant woman receives the COVID-19 vaccine from her doctor." src="https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425815/original/file-20211011-27-rprr7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Mothers infected with COVID-19 during pregnancy are twice as likely to lose their children shortly after birth, driving home the urgent need for pregnant women to get vaccinated.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/pregnant-woman-receives-a-dose-of-the-pfizer-biontech-news-photo/1234136159?adppopup=true">Raul Arboleda/AFP via Getty Images</a></span>
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<p>As a father of two, with a third expected in December, I understand the intense stress that health decisions can bring on during pregnancy. In dealing with our own high-risk pregnancy, my wife – who is a health care worker – was recently given the go-ahead to receive a Pfizer booster following its <a href="https://theconversation.com/fda-panel-recommends-limiting-pfizer-booster-shots-to-americans-65-and-older-and-those-at-high-risk-of-severe-covid-19-168224">recent FDA/CDC approval</a>. Even with high medical competency and <a href="https://doi.org/10.1084/jem.20132327">my own expertise as an immunologist</a>, I would be lying if I said the decision was an easy one. </p>
<p>Data is hard to listen to when it conflicts with our gut feelings, but that can be when people need it the most. In this case, the data is clear: COVID-19 poses a significant threat to both the mother and child, and vaccination can help mitigate that risk. </p>
<h2>The immunology of pregnancy is complicated</h2>
<p>Pregnancy is an immunological tightrope. At the most basic level, a maternal immune system’s job is to welcome a foreign organism that is consuming considerable resources, and allow it to grow unmolested for months. This doesn’t come naturally – to prevent the identification and rejection of a growing fetus as a parasitic invader, maternal immune systems <a href="https://doi.org/10.3389/fimmu.2020.575197">undergo an overhaul</a> that fundamentally alters their responses to infection in order to support the pregnancy.</p>
<p>But those changes don’t shut down immune responses completely. Compromising immune function to a point where infections are allowed to run rampant would not be a successful survival strategy for mother or child. </p>
<p>Instead, a new partnership is struck. The maternal immune systems <a href="https://doi.org/10.4049/jimmunol.178.6.3345">selectively chooses</a> not to react to foreign tissues and cells associated with the growing fetus, and instead enters into a <a href="https://dx.doi.org/10.1111%2Fj.1600-0897.2010.00836.x">coordinated dance</a>. Over the course of nine months, it will guide the attachment of the placenta to the uterine wall, promote growth and development of the fetus and ultimately <a href="https://doi.org/10.1038/cmi.2014.46">initiate labor</a> to kickoff the delivery.</p>
<p>This is complicated work and requires a measure of immuno-zen: An environment of calm and balance is carefully maintained around the uterus. But inflammation – a catch-all term used to describe the physical manifestations of intense immune activation – is a threat to that balance. Researchers have long understood that serious infectious diseases, which frequently trigger intense inflammatory immune responses throughout the body, pose a serious threat to the mother-fetus duo. The list of infectious diseases capable of complicating a pregnancy <a href="https://www.nichd.nih.gov/health/topics/pregnancy/conditioninfo/infections">is long</a>.</p>
<p>So it is not surprising that COVID-19, which can create chaos in normal immune responses through both <a href="https://dx.doi.org/10.3389%2Ffimmu.2020.01446">runaway inflammation</a> and <a href="https://doi.org/10.1101/2020.10.21.20216192">misdirected antibody responses</a>, has made that list.</p>
<h2>Vaccination protects both mother and child</h2>
<p>This balancing act that the immune system undergoes during pregnancy is precisely why vaccination is so important. While there is no doubt that <a href="https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html">getting a vaccine</a> activates the immune system – that’s exactly what it is supposed to do – this <a href="https://theconversation.com/vaccines-against-sars-cov-2-will-have-side-effects-thats-a-good-thing-151090">mild immune response</a> to the vaccine is nowhere close to the risks that the pregnancy faces if the mother contracts COVID-19.</p>
<p>When your body meets a harmless lookalike of SARS-CoV-2 in the form of the vaccine, <a href="https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html">the immune system is trained</a> to recognize the virus in a safe and controlled environment – without the threat of an actual COVID-19 infection. This way, if you encounter the real virus, your immune system is much more prepared and capable of fending it off. As a result, your immune system will be less likely to need to resort to the high-inflammation, <a href="https://theconversation.com/an-autoimmune-like-antibody-response-is-linked-with-severe-covid-19-146255">high-risk tactics</a> that it would have to deploy against severe infection. </p>
<p>Even with a vaccine that is not 100% effective due to <a href="https://doi.org/10.1016/S0140-6736(21)02183-8">waning antibodies</a> or the emergence of the <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html">delta variant</a>, studies have shown that the reduction of symptoms associated with partial protection is enough to <a href="https://doi.org/10.1001/jamapediatrics.2021.1050">lower the risk</a> of poor outcomes in both mother and child.</p>
<h2>COVID-19 vaccines protect the baby too</h2>
<p>In addition to the maternal protection that vaccines offer, <a href="https://doi.org/10.1016/j.ajogmf.2021.100481">a new study</a> has revealed that antibodies created in response to COVID-19 vaccination can also be effectively passed to the baby through umbilical cord blood. This finding is critical because while COVID-19 infections have not been shown to directly infect the fetus in utero, an infection can be passed from mother to child during birth. </p>
<p>In one study, nearly 15% of children <a href="https://doi.org/10.1001/jamapediatrics.2021.1050">delivered by Cesarean section</a> to COVID-19-infected mothers tested positive for the virus after birth. In this early stage of life, newborns do not yet possess the ability to produce antibodies effectively on their own. Instead, they are entirely reliant on mom – holding onto antibodies that were shared between them in the blood before birth, and getting new ones transferred through breastmilk. </p>
<p><a href="https://theconversation.com/pregnant-or-worried-about-infertility-get-vaccinated-against-covid-19-166535">Medical decisions around pregnancy are hard</a>, and the urge to protect the pregnancy by just leaving it alone is a strong one. It can feel like the small risks associated with vaccination are avoidable – so why take the chance? The problem, of course, is that the virus does not allow you to choose. Opting not to vaccinate is, unfortunately, a choice to roll the dice with a virus that has <a href="https://covid19.who.int/">killed millions</a> and has led to <a href="https://covid.cdc.gov/covid-data-tracker/#pregnant-population">catastrophic outcomes</a> for both mother and child.</p>
<p>COVID-19 vaccines have been shown to be <a href="https://doi.org/10.1016/j.ajogmf.2021.100464">safe and effective during pregnancy</a>. And now, research has made it clear that they can be an ally to the maternal immune system, helping it to maintain a healthy and balanced environment for a thriving pregnancy.</p>
<p>[<em>Research into coronavirus and other news from science</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-research">Subscribe to The Conversation’s new science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/169232/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Woodruff's research is supported by the National Institute of Health. He is a co-founder of Jefferson's Electorate. </span></em></p>In light of mounting research showing the serious risks of contracting COVID-19 during pregnancy, the CDC is re-upping its urgency that pregnant women get their shots.Matthew Woodruff, Instructor of Human Immunology, Emory UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1687032021-09-25T11:52:47Z2021-09-25T11:52:47ZTense decision-making as CDC joins FDA in recommending Pfizer booster shot for 65 & up, people at high risk and those with occupational exposure to COVID-19<figure><img src="https://images.theconversation.com/files/423190/original/file-20210924-3841-1shex90.jpg?ixlib=rb-1.1.0&rect=331%2C53%2C4796%2C3172&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The FDA and CDC are recommending use of a third shot, or "booster dose" for certain groups of people in the U.S.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/syringes-wand-vials-of-the-pfizer-biontech-covid-19-vaccine-news-photo/1230186505?adppopup=true"> Patrick T. Fallon/AFP via Getty Images</a></span></figcaption></figure><p>Following the <a href="https://theconversation.com/fda-panel-recommends-limiting-pfizer-booster-shots-to-americans-65-and-older-and-those-at-high-risk-of-severe-covid-19-168224">recommendations of its vaccine advisory committee</a>, the Food and Drug Administration <a href="https://www.fda.gov/news-events/press-announcements/fda-authorizes-booster-dose-pfizer-biontech-covid-19-vaccine-certain-populations">gave emergency use authorization</a> to Pfizer-BioNTech’s COVID-19 vaccine booster dose for certain populations. The single shot is to be administered six months following completion of the original two-dose course.</p>
<p>The FDA’s Sept. 22, 2021, decision to not extend boosters to the general population – at least not yet – was a <a href="https://apnews.com/article/joe-biden-health-coronavirus-pandemic-404cf650431f8aeee17d333180760337">direct rebuke</a> to the Biden administration’s announcement in August that booster shots would be rolled out to all eligible Americans beginning in late September. Biden’s pledge had been widely criticized for <a href="https://www.cnn.com/2021/08/31/health/fda-vaccine-officials-step-down/index.html">getting out in front of the science</a> and the regulatory process.</p>
<p>The FDA instead limited its authorization of the third Pfizer dose to people 65 and older, people ages 18-64 at high risk of severe COVID-19 due to pre-existing conditions, and individuals with frequent risk of exposure to the coronavirus through their work, such as health care workers and teachers. </p>
<p>The Centers for Disease Control and Prevention’s <a href="https://www.cdc.gov/vaccines/acip/index.html">Advisory Committee on Immunization Practices</a> then issued its own booster recommendations on Sept. 23, 2021. Its guidance aligned with the FDA’s authorization of boosters for use in ages 65 and up and people at high risk of severe COVID-19, but stopped short of endorsing booster shots for people with frequent occupational exposure. However, in an effort to realign the two agencies’ recommendations, CDC director Dr. Rochelle Walensky <a href="https://www.nytimes.com/2021/09/24/world/covid-boosters-vaccine-cdc-director.html">overrode the CDC advisory committee</a>, <a href="https://www.cdc.gov/media/releases/2021/p0924-booster-recommendations-.html">providing the go-ahead</a> for all groups listed under the FDA’s emergency use authorizations – including those with increased job-site risk. </p>
<p>Despite the mixed messaging between the agencies, the immediate effect is that millions of Americans will be in line for added protection amid concerns over <a href="https://www.nature.com/articles/d41586-021-02532-4">waning vaccine immunity</a>. An ongoing evaluation of whether COVID-19 boosters should be administered more broadly among vaccine-eligible people is <a href="https://www.statnews.com/2021/09/24/biden-covid-19-boosters-pitting-white-house-against-scientific-advisers/">likely to take place in the coming months</a>, as more data becomes available to inform questions of safety, need and efficacy of boosters.</p>
<h2>Fault lines between the FDA and CDC</h2>
<p>This fraught booster approval process may strike some as strange, as the FDA is solely responsible for drug approval <a href="https://doi.org/10.1001/jama.2021.11558">in most contexts</a>. However, as the body responsible for managing U.S. public vaccination programs, the CDC’s approval is required in order to begin the distribution and administration of vaccines.</p>
<p>The close intersection of the two agencies in approval and distribution of vaccines has recently become a point of contention for some high level officials, with <a href="https://www.cnn.com/2021/08/31/health/fda-vaccine-officials-step-down/index.html">two senior FDA vaccine leaders resigning</a> from their posts in early September 2021. One former FDA leader cited the expanding role of the CDC in vaccine evaluation as <a href="https://endpts.com/breaking-in-a-major-blow-to-vaccine-efforts-senior-fda-leaders-stepping-down-report/">a major reason for their departure</a>.</p>
<p>The tensions between these agencies was on full display when the CDC’s advisory committee excluded high occupational exposure risk as a booster-eligible group, <a href="https://thehill.com/policy/healthcare/573707-cdc-panel-authorizes-covid-19-vaccine-boosters">breaking from the FDA recommendation and authorization</a>. The committee’s vote to not authorize boosters for those with frequent occupational exposures stemmed primarily from concerns that the recommendation was overly broad – potentially leading to confusion as to who counts as a worker at “high risk.” </p>
<p>This, combined with a shared view – <a href="https://doi.org/10.1016/S0140-6736(21)02046-8">including among some public health officials</a> – that critical pieces of data being used to advocate for the booster in the broader population were <a href="https://www.cnbc.com/2021/08/30/booster-shot-cdc-scientist-says-theres-limited-data-to-evaluate-covid-shot-for-general-population.html">incomplete and open to interpretation</a>, resulted in a 9-6 vote from the CDC committee <a href="https://www.statnews.com/2021/09/23/covid19-vaccine-boosters-cdc-acip">against the third dose</a> for those at increased occupational risk. </p>
<h2>Back in alignment</h2>
<p>Ultimately, Walensky’s decision to side with the FDA on extending boosters to those with frequent occupational exposure – such as health care workers and teachers – brings the two agencies into alignment. And while it still falls short of the Biden administration’s pledge of boosters for all vaccine-eligible people in the U.S., the decision will pave the way for millions of third Pfizer doses to be administered in the coming months. </p>
<p>“As CDC Director, it is my job to recognize where our actions can have the greatest impact. At CDC, we are tasked with analyzing complex, often imperfect data to make concrete recommendations that optimize health. In a pandemic, even with uncertainty, we must take actions that we anticipate will do the greatest good,” <a href="https://www.cdc.gov/media/releases/2021/p0924-booster-recommendations-.html">Walensky said in a statement</a>.</p>
<p>More guidance on COVID-19 boosters is expected to be issued soon for people who received the <a href="https://www.nbcchicago.com/news/coronavirus/johnson-johnson-moderna-and-pfizer-what-we-know-about-booster-shots-so-far/2618188/">Moderna</a> and <a href="https://theconversation.com/new-johnson-johnson-data-shows-second-shot-boosts-antibodies-and-protection-but-one-dose-is-still-strong-against-delta-168463">Johnson & Johnson</a> vaccines.</p>
<p>[<em>Research into coronavirus and other news from science</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-research">Subscribe to The Conversation’s new science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/168703/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Woodruff's research is supported by the US National Institute of Health. He is a co-founder of Jefferson's Electorate.</span></em></p>Fault lines between the FDA and CDC regulatory processes have been on full display in the decisions over which groups of Americans should receive the Pfizer booster shot.Matthew Woodruff, Instructor of Human Immunology, Emory UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1682242021-09-17T21:30:30Z2021-09-17T21:30:30ZFDA panel recommends limiting Pfizer booster shots to Americans 65 and older, and those at high risk of severe COVID-19<figure><img src="https://images.theconversation.com/files/421927/original/file-20210917-25-1arptol.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3303%2C2190&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">No third dose for now.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakBooster/2591977a51e545daad893fd64a8d699f/photo?Query=vaccine%20AND%20panel&mediaType=photo&sortBy=arrivaldatetime:desc&dateRange=Anytime&totalCount=76&currentItemNo=0">AP Photo/Robert F. Bukaty</a></span></figcaption></figure><p>The key scientific advisory council of the Food and Drug Administration has <a href="https://www.nytimes.com/live/2021/09/17/world/covid-delta-variant-vaccine">voted to deny</a> use of a “booster” shot of Pfizer’s mRNA vaccine to the general public – a move that will likely disappoint some <a href="https://www.cnn.com/2021/09/16/health/covid-19-boosters-agencies-khn-partner/index.html">public health experts pushing for a third dose</a> to help slow the spread of COVID-19.</p>
<p>In a 16-2 vote on Sept. 17, 2021, an independent committee of physicians, scientists and public health experts recommended against full use of the third dose of the vaccine, which now goes by the brand name “Comirnaty.” However, the panel did recommend the shot for Americans age 65 and older or those at high risk for severe COVID-19. In recommending against the shot for the general public, the committee cited reasons such as lack of sufficient safety data in younger age groups as well as indications that the initial doses still seem to be providing robust protection against severe illness leading to hospitalization and death. The panel also agreed in a poll – but not a formal vote – that boosters would be beneficial for certain populations, such as health care workers and others at high risk for occupational exposure.</p>
<p>Although the vote is not binding, it is likely that it will form the basis of a formal FDA recommendation.</p>
<p>As <a href="https://scholar.google.com/citations?user=-oDHlFYAAAAJ&hl=en">an immunologist</a> who <a href="https://doi.org/10.1038/s41590-020-00814-z">studies COVID-19</a> and <a href="https://doi.org/10.1016/j.celrep.2018.09.029">immune responses to vaccination</a>, I saw the push for a booster as predictable, although the outcome of the vote was always far from certain. Over the past year, <a href="https://doi.org/10.1056/nejmc2032195">significant research</a> and <a href="https://www.nytimes.com/2021/06/28/health/coronavirus-vaccines-immunity.html">public reporting</a> have focused on the durability of the immune response following the first and second doses of the COVID-19 mRNA vaccines. This work has been critical to scientists’ understanding of how long the immune responses from vaccination can provide protection, and whether that protection extends to new and emerging variants of the SARS-CoV-2 virus.</p>
<h2>Waning antibodies</h2>
<p>The good news is that the mRNA vaccines do appear to provide <a href="https://doi.org/10.1056/nejmoa2108891">continued efficacy</a> against serious illness or death caused by new strains of the coronavirus, including the highly infectious <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html">delta variant</a>.</p>
<p>But data on the longevity of this protection has been more mixed and is still limited in scope. Although there are indications that immune “memory” <a href="https://doi.org/10.1038/s41586-021-03738-2">is being established</a> in vaccine recipients – almost certainly providing partial protection in the long term – the antibodies responsible for stopping the virus in its tracks before infection occurs appear to <a href="https://doi.org/10.1016/j.lanepe.2021.100208">wane over the course of months</a> following the second dose.</p>
<p>This is not surprising to immunologists and does not mean the vaccine isn’t working. Antibodies wane as a normal course of an immune response to any vaccine. This is why you need a tetanus booster every decade or so, and why the measles, mumps and rubella vaccine is administered in three doses – not just two.</p>
<p>The question is simply how fast antibodies decline, and at what point they no longer provide adequate protection. At that point, an additional dose of the vaccine is recommended to “boost” the antibody numbers back up to protective levels. In this case, widespread reporting of <a href="https://www.cdc.gov/vaccines/covid-19/health-departments/breakthrough-cases.html">breakthrough infections</a> – infections in individuals who have been fully vaccinated – and research citing the <a href="http://dx.doi.org/10.15585/mmwr.mm7034e4">possibility of declining immunity</a> in populations vaccinated early in the pandemic brought discussions of the need for boosters quickly to the forefront.</p>
<p>Against this backdrop of mixed data, the FDA panel had to weigh the risks and benefits surrounding booster shots. While the third dose of vaccine would have been identical to those already <a href="https://www.fda.gov/news-events/press-announcements/fda-approves-first-covid-19-vaccine">fully approved</a> – and as such <a href="https://doi.org/10.1056/nejmoa2110475">deemed safe</a> – they would not be without <a href="https://theconversation.com/vaccines-against-sars-cov-2-will-have-side-effects-thats-a-good-thing-151090">side effects</a> similar to those seen in the first and second doses.</p>
<p>In addition, serious conditions <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html">such as myocarditis</a> – an inflammation of the heart – that have been recorded in rare and isolated cases after the initial vaccine shots will likely occur following the booster as well. This, in addition to a debate around the absolute benefit of a third shot to maintain current protection levels in otherwise healthy vaccinated individuals, has led many public health officials to <a href="https://doi.org/10.1016/S0140-6736(21)02046-8">express concern</a> that the review is premature and risks further confusing and alienating an <a href="https://www.kff.org/policy-watch/the-red-blue-divide-in-covid-19-vaccination-rates/">already divided American public</a>.</p>
<h2>Separating politics from data</h2>
<p>With the Biden administration having <a href="https://www.businessinsider.com/fda-cdc-heads-push-back-on-bidens-covid-19-booster-shot-plan-2021-9">already publicly backed a third dose</a> for all vaccinated Americans in August, the committee was tasked with separating the politics from the data to weigh in on whether the benefits of a booster shot outweighed the risks to an already-hesitant American public.</p>
<p>In rejecting the proposal, the FDA panel has signaled its confidence in the original vaccination course among healthy individuals, and will wait for additional data before identifying waning antibody levels as a significant threat to public safety. However, its support for boosting those at high risk for exposure to COVID-19 suggests a recognition that additional shots may yet be necessary to fully protect the public at large.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p><img src="https://counter.theconversation.com/content/168224/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Woodruff's research is supported by the National Institute of Health, and is a co-founder of Jefferson's Electorate. </span></em></p>An FDA panel has voted against recommending approval of a booster COVID-19 shot for the general population – disappointing some public health officials.Matthew Woodruff, Instructor of Human Immunology, Emory UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1675852021-09-16T11:51:51Z2021-09-16T11:51:51ZQ+A: COVID vaccine boosters – who will receive them and why are they being given?<figure><img src="https://images.theconversation.com/files/421573/original/file-20210916-17-pr74c2.jpg?ixlib=rb-1.1.0&rect=60%2C231%2C6720%2C3953&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/male-doctor-next-elderly-woman-covid19-2032063490">ShotPrime Studio/Shutterstock</a></span></figcaption></figure><p>After consulting its vaccine advisers, the UK government is <a href="https://www.gov.uk/government/publications/jcvi-statement-september-2021-covid-19-booster-vaccine-programme-for-winter-2021-to-2022/jcvi-statement-regarding-a-covid-19-booster-vaccine-programme-for-winter-2021-to-2022">launching</a> its much-discussed COVID-19 vaccine booster programme. From the <a href="https://www.bbc.co.uk/news/health-58550833">week beginning</a> September 20 2021, a third dose will be offered to all people who were prioritised in the first wave of the UK’s vaccine rollout.</p>
<p>This includes all residents and staff of care homes, all frontline health and social care workers, everyone over 50, all those over 16 who have underlying health conditions that put them at higher risk of severe COVID-19 (together with their carers) and all adults who live with an immunosuppressed person.</p>
<p>Anyone taking a third dose will need to have had their second at least six months previously, and people will be prioritised <a href="https://www.gov.uk/government/publications/covid-19-vaccination-care-home-and-healthcare-settings-posters/covid-19-vaccination-first-phase-priority-groups">as in the first wave</a> of the vaccine rollout, with care home residents and staff to be vaccinated first. If you or someone you know is going to be included in the booster programme, here are the key things you need to know.</p>
<h2>Why are boosters being given?</h2>
<p>Because there are worries that some of the effects of the first two doses may have worn off for those that received their vaccines a while ago. Boosters can solve this problem by reminding the immune system to be ready to deal with an infection – they top up immunity.</p>
<p>Whether people who had the vaccine over six months ago actually need their immunity topping up isn’t clear cut. There’s <a href="https://theconversation.com/covid-vaccine-effects-wane-over-time-but-still-prevent-death-and-severe-illness-167587">some evidence</a> that COVID-19 vaccine protection fades over time, but the vaccines are too new to be sure of whether this will continue in such as way as to leave people at risk. Therefore, the British government is offering boosters as a precaution.</p>
<p>Its <a href="https://www.gov.uk/government/publications/jcvi-statement-september-2021-covid-19-booster-vaccine-programme-for-winter-2021-to-2022/jcvi-statement-regarding-a-covid-19-booster-vaccine-programme-for-winter-2021-to-2022">fear</a> is that if the immunity of those who were vaccinated earliest has waned and continues to do so, many could get sick over the winter when indoor mixing (and so the risk of transmission) increases. Remember that those vaccinated longest ago are also those most vulnerable to COVID-19.</p>
<p>As well as costing lives, if there was a spike of disease in this group, this could combine with other seasonal pressures (such as influenza and other viral diseases) to overwhelm the NHS.</p>
<h2>What vaccine will people get?</h2>
<p>Probably Pfizer/BioNTech.</p>
<p>The Joint Committee on Vaccination and Immunisation has recommended that this should be given to everyone. It made this recommendation after reviewing unpublished data from the <a href="https://www.covboost.org.uk/home">Cov-Boost Study</a>, which has been investigating the effects of using different vaccines as boosters.</p>
<p>According to the committee, the Cov-Boost Study has shown that the Pfizer jab produces a good boost regardless of which vaccine was used previously. Indeed, <a href="https://theconversation.com/covid-vaccines-combining-astrazeneca-and-pfizer-may-boost-immunity-new-study-163667">previous research</a> has suggested that boosting an Oxford/AstraZeneca dose with a Pfizer one may lead to a stronger immune response than following it with another AstraZeneca. Mixing manufacturers like this is safe and possibly even advantageous.</p>
<p>The Cov-Boost Study revealed that a half dose of the Moderna vaccine also performs well as a booster and so can be offered too. If necessary, the committee says that AstraZeneca can also be used as a booster, but only in those who received it previously.</p>
<p>There may be an interesting knock-on effect of these decisions. The Pfizer and Moderna vaccines need to be stored in freezers, and so the logistics of distributing them are more difficult than for the AstraZeneca jab, which only needs refrigerating.</p>
<p>Prioritising using these more difficult-to-distribute vaccines for the UK’s booster programme could free up the more easy-to-store AstraZeneca doses to be sent overseas to places where maintaining freezing temperatures is difficult. The UK is planning to donate <a href="https://www.gov.uk/government/publications/covid-19-response-autumn-and-winter-plan-2021/covid-19-response-autumn-and-winter-plan-2021">close to 20 million vaccine doses</a> to other countries between now and the end of 2021.</p>
<h2>Is launching a booster programme the right thing to do?</h2>
<p>While it isn’t wholly clear to what extent vaccine protection wanes, we do know that immunity to other coronaviruses tends to be lost after a while. In some people it may only last a <a href="https://academic.oup.com/jid/article/223/3/409/5868459">few months</a>. Waning protection is definitely plausible.</p>
<p>Plus, some people in the first wave of vaccinations will have had underperforming immune systems due to illness or medical treatment, which may have <a href="https://theconversation.com/how-will-covid-vaccines-work-on-compromised-immune-systems-heres-what-we-know-164107">lowered the amount of protection</a> that COVID-19 vaccines offered them. The immune response also declines as you get older, rendering vaccines less protective. So it makes sense to give a booster to those currently being prioritised.</p>
<p>However, there’s <a href="https://www.science.org/doi/full/10.1126/sciimmunol.abj1750">good evidence</a> that the body can make a strong and lasting response to the COVID-19 vaccines. In normal healthy adults, a full course of the vaccine (usually two doses) should be enough. Younger, generally healthy people who have been fully vaccinated can get ill with COVID-19 but are unlikely to <a href="https://www.mja.com.au/journal/2021/215/4/effectiveness-covid-19-vaccines-findings-real-world-studies">need an emergency trip to hospital</a>. There’s little to support widening Britain’s booster programme any further.</p>
<p>The coronavirus will not be under control until everyone in the world is protected. This raises the question of <a href="https://www.standard.co.uk/news/politics/covid-vaccine-booster-david-nabarro-world-health-organisation-covax-b954672.html">whether it’s right</a> to give any boosters to people who have already been double vaccinated, when healthcare workers in many countries have not even had a first COVID-19 vaccine dose. Certainly, boosters should not be given where they aren’t really needed.</p>
<p>At this point in the pandemic, at the very least we should be offering boosters and increasing the pace of vaccine rollout across the world. It ought to be possible to do both. But if it isn’t, we should be prioritising those who are most vulnerable.</p><img src="https://counter.theconversation.com/content/167585/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Pitt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The UK has outlined plans to top the immunity of the most vulnerable ahead of the winter.Sarah Pitt, Principal Lecturer, Microbiology and Biomedical Science Practice, Fellow of the Institute of Biomedical Science, University of BrightonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1669612021-09-07T00:50:02Z2021-09-07T00:50:02ZWhen will I need my COVID vaccine booster shot? And can I switch to a different brand?<p>Australia’s vaccine rollout is really starting to gain pace, especially in <a href="https://www.nsw.gov.au/covid-19/find-the-facts-about-covid-19#vaccination-totals-to-date">New South Wales</a> and <a href="https://twitter.com/CaseyBriggs/status/1434770049978363907">Victoria</a>. </p>
<p>We need to get two doses of vaccine into as many adults as possible — firstly because that helps reduce severity of illness and infection, but also because reaching vaccination targets is likely to bring some new freedoms.</p>
<p>The COVID-19 vaccines (Pfizer, Moderna and Astra Zeneca) continue to be highly effective in reducing risk of severe disease, hospitalisation and death, even against the Delta variant. </p>
<p>But as soon as we finish one vaccine rollout we may need to begin the next rollout of booster doses.</p>
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Read more:
<a href="https://theconversation.com/why-is-a-third-covid-19-vaccine-dose-important-for-people-who-are-immunocompromised-166569">Why is a third COVID-19 vaccine dose important for people who are immunocompromised?</a>
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<h2>When will I need my booster shot?</h2>
<p>First, we need to differentiate between a booster dose and a third dose as part of the initial round of vaccinations. They are two very different things.</p>
<p>Some people who are <a href="https://www.medscape.com/viewarticle/957963?src=WNL_dne_210902_mscpedit&uac=82473HY&impID=3609450&faf=1">immunosupressed</a> might need a <a href="https://www.gov.uk/government/publications/third-primary-covid-19-vaccine-dose-for-people-who-are-immunosuppressed-jcvi-advice/joint-committee-on-vaccination-and-immunisation-jcvi-advice-on-third-primary-dose-vaccination">third dose</a> as part of their primary COVID-19 vaccination schedule. In other words, their third dose comes not long after their second dose and is given to improve their initial protection. </p>
<p>A booster shot is given much later after the initial two dose round of shots. A good example is the way we give tetanus and whooping cough booster vaccines. </p>
<p>There’s a great explainer on who might need a third dose as part of their primary vaccination schedule over <a href="https://theconversation.com/why-is-a-third-covid-19-vaccine-dose-important-for-people-who-are-immunocompromised-166569">here</a>. </p>
<p>For the rest of us, we don’t know for sure when you will need a booster shot. You’ll read lots of different figures on this — six months, eight months, more — and that’s because the research is ongoing. We don’t yet have a definite answer to the best timing for a booster dose. </p>
<p>Pfizer recently <a href="https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-submission-initial-data-us-fda">announced</a> its research had shown a booster dose resulted an increase in antibodies against the initial virus as well as against the highly infectious Delta variant. These results are awaiting publication and the safety of the booster dose needs to be known. The European regulator (known as the European Medicines Agency) has also started to evaluate an application for the use of a <a href="https://www.ema.europa.eu/en/news/ema-evaluating-data-booster-dose-covid-19-vaccine-comirnaty">booster dose of the Pfizer vaccine</a>.</p>
<p>We know that there is a <a href="https://theconversation.com/how-long-does-immunity-last-after-covid-vaccination-do-we-need-booster-shots-2-immunology-experts-explain-164073">decline in antibodies</a> after the primary course and some evidence of <a href="https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-08-30/09-COVID-Oliver-508.pdf">waning protection against infection</a>. </p>
<p>In a recent letter to <a href="https://www.nejm.org/doi/full/10.1056/NEJMc2112981?query=featured_home">The New England Journal of Medicine</a>, published online earlier this month, doctors and public health experts at University of California San Diego said their data suggested vaccine effectiveness against any symptomatic disease may wane over time since vaccination:</p>
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<p>Vaccine effectiveness exceeded 90% from March through June but fell to 65.5% […] in July.</p>
</blockquote>
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Read more:
<a href="https://theconversation.com/how-long-does-immunity-last-after-covid-vaccination-do-we-need-booster-shots-2-immunology-experts-explain-164073">How long does immunity last after COVID vaccination? Do we need booster shots? 2 immunology experts explain</a>
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<p>Over time, data will emerge on immune responses and safety after a booster dose. </p>
<p>It may be that booster doses are particularly needed for certain groups in our community — for example, older people or frontline workers. There is also discussion of whether severely immunosuppressed people should get a booster dose from around six months after their third primary dose. </p>
<p>The US is planning to make <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html">COVID booster shots</a> widely available to Americans <a href="https://www.reuters.com/world/us/us-begin-offering-covid-19-vaccine-booster-shots-september-2021-08-18/">from September</a> onwards, starting <a href="https://www.cnbc.com/2021/08/18/covid-booster-shots-us-to-begin-wide-distribution-of-third-vaccine-doses-next-month.html">eight months</a> after people’s second dose of the Pfizer or Moderna vaccines. </p>
<p>The US booster plan is dependent on the Food and Drug Administration <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html">determining that a third dose</a> of the two-dose vaccines is safe and effective, and following advice from the Centers for Disease Control.</p>
<p>Israel’s booster rollout has begun, with people there becoming eligible for a booster <a href="https://www.cnbcno.com/2021/08/30/israel-doubles-down-on-covid-booster-shots-as-breakthrough-cases-rise.html">five months</a> after their second dose.</p>
<p>The European Centre for Disease Prevention and Control recently <a href="https://www.ecdc.europa.eu/en/publications-data/covid-19-public-health-considerations-additional-vaccine-doses">said</a> that there is </p>
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<p>no urgent need for the administration of booster doses of vaccines to fully vaccinated individuals in the general population.</p>
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<h2>Can we mix and match, by getting a different brand of vaccine for the booster?</h2>
<p>We don’t yet know for sure. </p>
<p>There may be benefits to getting a different vaccine to the one you first got as a booster. We also know that new vaccines designed specifically to target novel variants are in development and it may be better to receive a booster of a variant-specific vaccine.</p>
<p>It will be worth keeping a close eye on a key trial by the UK-based <a href="https://www.covboost.org.uk/about">COV-BOOST</a> group, which is aiming to find out which vaccines against COVID-19 are most effective as a booster vaccination, depending on which vaccine was used to provide the initial primary vaccine course.</p>
<p>This study will give us good information on whether it will be better to get a booster shot that is the same brand as your primary dose, or whether to switch to another. </p>
<p>For example, should a person who initially got Pfizer for their first two doses get an AstraZeneca shot for their booster? Or vice versa? Or should they get a booster of a new variant vaccine?</p>
<p>A <a href="https://clinicaltrials.gov/ct2/show/NCT04889209%20term=moderna+variant&cond=Covid19&draw=2&rank=3">trial</a> is underway in the US looking at the safety and immune responses of using a different booster vaccine to the first two doses, but also includes a Beta (B.1.351) variant vaccine.</p>
<p>It’s possible <a href="https://theconversation.com/why-do-we-need-booster-shots-and-could-we-mix-and-match-different-covid-vaccines-155951">mixing and matching</a> different vaccines might <a href="https://www.science.org/news/2021/06/mixing-covid-19-vaccines-appears-boost-immune-responses">broaden your protection</a> — but the research is ongoing, and it’s too early to say.</p>
<p>Hopefully, supply chain issues for the Pfizer vaccine will improve in the coming months. </p>
<p>The prime minister recently <a href="https://www.pm.gov.au/media/four-million-pfizer-doses-arrive-super-charge-vaccine-roll-out">announced</a> Australia has secured an extra <a href="https://www.abc.net.au/news/2021-09-03/covid-19-vaccine-swap-pfizer-four-million-doses-from-uk/100431828">four million doses</a> as part of a deal with the UK, on top of <a href="https://www.pm.gov.au/media/four-million-pfizer-doses-arrive-super-charge-vaccine-roll-out">extra doses</a> coming as part of deals with Singapore and Poland. </p>
<p>This will help with the rollout of initial doses.</p>
<h2>For now, the priority is getting the two doses into arms</h2>
<p>Monitoring of the effectiveness of the COVID vaccines will continue, particularly against the delta variant and any new variants that emerge. </p>
<p>Trials are also underway of the safety and immune responses to a variety of different booster vaccines, including the next generation variant vaccines.</p>
<p>The World Health Organization <a href="https://www.who.int/news/item/10-08-2021-interim-statement-on-covid-19-vaccine-booster-doses">said</a> in August:</p>
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<p>In the context of ongoing global vaccine supply constraints, administration of booster doses will exacerbate inequities by driving up demand and consuming scarce supply while priority populations in some countries, or subnational settings, have not yet received a primary vaccination series. </p>
<p>The focus for the time being remains on increasing global vaccination coverage with the primary series.</p>
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<p>For now, Australia must focus on getting our primary adult coverage as high as possible in order to protect against severe disease, hospitalisation, and death.</p>
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Read more:
<a href="https://theconversation.com/why-well-get-covid-booster-vaccines-quickly-and-how-we-know-theyre-safe-156120">Why we'll get COVID booster vaccines quickly and how we know they're safe</a>
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<img src="https://counter.theconversation.com/content/166961/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Wood receives funding from the NHMRC for a Career Development Fellowship. He holds a Churchill Fellowship</span></em></p>You’ll read lots of different figures on this — six months, eight months, more — and that’s because the research is ongoing. We don’t yet have a concrete answer.Nicholas Wood, Associate Professor, Discipline of Childhood and Adolescent Health, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1665692021-08-31T20:01:19Z2021-08-31T20:01:19ZWhy is a third COVID-19 vaccine dose important for people who are immunocompromised?<figure><img src="https://images.theconversation.com/files/418577/original/file-20210831-25-4evegl.jpg?ixlib=rb-1.1.0&rect=19%2C0%2C6470%2C4173&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>A number of countries including <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-vaccine-dose-certain-immunocompromised">the United States</a> and <a href="https://www.gov.uk/government/news/jcvi-issues-interim-advice-on-covid-19-booster-vaccination">the United Kingdom</a> are moving to make a third dose of COVID-19 vaccine available to people who are immunocompromised.</p>
<p>But why are people with weaker immune systems at the front of the queue for a third dose?</p>
<p>As we continue to roll out COVID-19 vaccines around the world, emerging data is showing those who are immunocompromised aren’t necessarily as well protected by the first two doses.</p>
<p>So for these people, a third dose, sooner rather than later, could be particularly beneficial.</p>
<h2>First, who is ‘immunocompromised’?</h2>
<p>People who are immunocompromised have conditions called immunodeficiencies, where part of their immune system is missing or not functioning as well as it should. </p>
<p>Around <a href="https://jamanetwork.com/journals/jama/fullarticle/2572798">2.8% of adults in the US</a> are immunocompromised. We expect the rate is similar in Australia.</p>
<p>Immunodeficiencies are broadly divided into two categories:</p>
<ul>
<li><p><strong>primary immunodeficiencies</strong> are very rare, often inherited conditions caused by mutations in our DNA</p></li>
<li><p><strong>secondary immunodeficiencies</strong> are more common and are acquired after birth. Factors that can cause secondary immunodeficiency include malnutrition, certain infections, cancer, and some drug treatments. </p></li>
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Read more:
<a href="https://theconversation.com/why-do-we-need-booster-shots-and-could-we-mix-and-match-different-covid-vaccines-155951">Why do we need booster shots, and could we mix and match different COVID vaccines?</a>
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<p>Immunodeficiencies vary in severity, depending on what part of the immune system is missing or the degree of function lost. </p>
<p>The <a href="https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/immunocompetence.html">moderate to severe end of the spectrum</a> includes serious forms of primary immunodeficiencies, untreated human immunodeficiency virus (HIV) infection, organ or bone marrow transplant recipients, and people treated with chemotherapy or high doses of immunosuppressive drugs. </p>
<p>We know severely immunocompromised people are susceptible to <a href="https://www.nature.com/articles/s41586-020-2521-4">more severe</a> and <a href="https://www.nejm.org/doi/full/10.1056/nejmc2031364">prolonged illness</a> with COVID-19.</p>
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<img alt="A man receives a vaccination." src="https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=316&fit=crop&dpr=1 600w, https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=316&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=316&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=398&fit=crop&dpr=1 754w, https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=398&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/418575/original/file-20210831-25-1f7a0of.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=398&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A person undergoing cancer treatment could be immunocompromised.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bald-male-patient-cancer-talking-mature-1911956239">Shutterstock</a></span>
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<h2>How well do COVID-19 vaccines work in immunocompromised people?</h2>
<p>A <a href="https://khub.net/documents/135939561/430986542/RCGP+VE+riskgroups+paper.pdf/a6b54cd9-419d-9b63-e2bf-5dc796f5a91f">preprint</a> (a study yet to undergo peer review) from the UK shows the Pfizer and AstraZeneca vaccines are 73% and 74.6% effective in preventing symptomatic COVID-19 in immunocompromised people respectively.</p>
<p>However, several <a href="https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(21)00367-0/fulltext">published</a> and <a href="https://www.medrxiv.org/content/10.1101/2021.07.08.21259776v1">emerging</a> studies are reporting that people who are severely immunocompromised have very high rates of “breakthrough” infections (where people become infected despite being fully vaccinated). This clearly signals COVID-19 vaccines aren’t working optimally in this group.</p>
<p>Some people with primary immunodeficiencies can generate <a href="https://www.jacionline.org/article/S0091-6749(21)00887-3/fulltext">immune responses to COVID-19 vaccines</a>, but these responses tend to be lower than what we’re seeing in healthy people. This decreased immunity could lead to increased breakthrough infections.</p>
<p>Normally, after one dose of the Pfizer vaccine, <a href="https://www.sciencedirect.com/science/article/pii/S1198743X21002895">nearly 100% of healthy people</a> will make detectable levels of antibodies against the virus.</p>
<p>But in <a href="https://www.nejm.org/doi/full/10.1056/NEJMc2108861">a trial with organ transplant recipients</a>, only 4% of people generated a detectable immune response after one dose, increasing to 40% after two doses and 68% after three doses. </p>
<p>So a third dose is likely to provide significant benefit to severely immunocompromised patients.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-dont-yet-know-how-effective-covid-vaccines-are-for-people-with-immune-deficiencies-but-we-know-theyre-safe-and-worthwhile-155741">We don't yet know how effective COVID vaccines are for people with immune deficiencies. But we know they're safe — and worthwhile</a>
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</p>
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<p>Notably, immunocompromised people are already <a href="https://immunisationhandbook.health.gov.au/vaccination-for-special-risk-groups/vaccination-for-people-who-are-immunocompromised">given additional doses of some vaccines</a>. </p>
<p>For example, it’s recommended people who have received a bone marrow transplant <a href="https://immunisationhandbook.health.gov.au/resources/handbook-tables/table-recommendations-for-revaccination-after-haematopoietic-stem-cell">receive two doses of the influenza vaccine</a> in the first year after the transplant, instead of the usual single dose.</p>
<h2>What about third doses in other people?</h2>
<p>In addition to classic immunodeficiencies, ageing can lead to a modest immune deficit. In turn, older people are more susceptible to some infections, <a href="https://www.nature.com/articles/s41586-020-2521-4">including COVID-19</a>.</p>
<p>Studies with the Pfizer vaccine show <a href="https://wwwnc.cdc.gov/eid/article/27/8/21-1145_article">immune responses are lower in older people</a> compared to younger people. Pfizer has shared early data showing <a href="https://s21.q4cdn.com/317678438/files/doc_financials/2021/q2/Q2-2021-Earnings-Charts-FINAL.pdf">a third dose of their vaccine can increase immunity</a> in 65 to 85-year-olds.</p>
<p>Some countries are starting to offer third doses to older people. For example, Israel started delivering third doses to <a href="https://www.washingtonpost.com/world/middle_east/pfizer-israel-booster-third-dose/2021/07/29/8c5b2170-efe5-11eb-81b2-9b7061a582d8_story.html">people over 60 in late July</a> (before opening boosters up to <a href="https://www.haaretz.com/israel-news/israel-to-expand-covid-booster-shots-to-anyone-over-40-1.10133544">younger age groups</a> during August). </p>
<p>However, double and even single doses of the Pfizer or AstraZeneca vaccines <a href="https://www.sciencedirect.com/science/article/pii/S1473309921003303?via%3Dihub">very effectively protect</a> against severe disease with COVID-19 among older people. So it’s still unclear whether this is urgently needed.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1430567492536217602"}"></div></p>
<p>A third dose for all ages could ultimately be used to generate optimal immunity against COVID-19. Some preprint studies suggest <a href="https://www.ndm.ox.ac.uk/files/coronavirus/covid-19-infection-survey/finalfinalcombinedve20210816.pdf">immunity can modestly decline</a> by about three months after the second dose.</p>
<p>Pfizer has shared preliminary data showing a <a href="https://s21.q4cdn.com/317678438/files/doc_financials/2021/q2/Q2-2021-Earnings-Charts-FINAL.pdf">third dose can boost immunity</a> in healthy people. </p>
<p>But the rollout of third doses to a broader range of people in higher-income countries has implications for vaccine equity. The World Health Organization Director General, Tedros Adhanom Ghebreyesus, has led calls to <a href="https://www.abc.net.au/news/2021-08-24/who-tedros-adhanom-ghebreyesus-vaccine-booster-moratorium/100401328">pause third doses</a> until more people in lower and middle income countries are able to access vaccines. </p>
<p>However, he specified <a href="https://www.npr.org/2021/08/23/1030248514/who-calls-for-a-delay-in-booster-shots-to-prioritize-under-vaccinated-countries">immunocompromised people should have access</a> to a third dose.</p>
<h2>When might third doses be offered in Australia?</h2>
<p>In Australia, a third dose of a vaccine may be offered to immunocompromised people, and possibly eventually to everyone. Some media reports have suggested <a href="https://www.abc.net.au/news/2021-08-25/pfizer-moderna-covid-vaccine-booster-shots-for-australia/100393856">this may be months away</a>. Health Minister Greg Hunt has indicated <a href="https://www.health.gov.au/ministers/the-hon-greg-hunt-mp/media/press-conference-in-melbourne-on-29-july-2021-about-the-covid-19-vaccine-rollout-and-the-covid-19-outbreak-in-nsw">current vaccine agreements</a> have factored in the possibility of boosting. </p>
<p>A shift to third doses would need approval from the Australian regulatory and vaccine advisory bodies, and would probably focus on immunocompromised and other high-risk people initially.</p>
<p>A third dose of a variant-specific vaccine could also be an option in the future. These vaccines can deliver an updated version of the virus “antigen” — the target our immune system learns to recognise on the surface of the virus — to refocus our immune system on new strains like Delta. </p>
<p>This approach would be similar to our yearly update of the flu vaccine. <a href="https://clinicaltrials.gov/ct2/show/NCT04368728?term=BioNTech+variant&cond=covid&draw=2&rank=8">Pfizer</a>, <a href="https://clinicaltrials.gov/ct2/show/NCT04785144?term=mRNA-1273.351&draw=2&rank=1">Moderna</a> and other vaccine manufacturers have variant-specific COVID-19 vaccines in clinical testing.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/immunocompromised-people-make-up-nearly-half-of-covid-19-breakthrough-hospitalizations-an-extra-vaccine-dose-may-help-166241">Immunocompromised people make up nearly half of COVID-19 breakthrough hospitalizations – an extra vaccine dose may help</a>
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<p>Even with a third dose, other measures will continue to be important in protecting immunocompromised people from COVID-19. These include “shielding” (staying at home and minimising face-to-face contact with others), immunoglobulin replacement treatment (which replaces antibodies needed to fight disease), and high vaccine uptake among the rest of the community. </p>
<p>But it’s clear a third dose would be uniquely beneficial for this group.</p><img src="https://counter.theconversation.com/content/166569/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emily Edwards is Vice President of AusPIPS (Australian Primary Immunodeficiency Patient Support group) Inc.</span></em></p><p class="fine-print"><em><span>Kylie Quinn receives funding from the Rebecca L. Cooper Foundation, the CASS Foundation, the Medical Research Future Fund and RMIT University.
</span></em></p>As we continue to roll out COVID-19 vaccines around the world, we’re learning people who are immunocompromised aren’t necessarily protected as well from the first two doses.Emily Edwards, Research fellow, Allergy and Clinical Immunology Laboratory, Monash UniversityKylie Quinn, Vice-Chancellor's Research Fellow, School of Health and Biomedical Sciences, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1659602021-08-27T12:29:53Z2021-08-27T12:29:53ZVaccines could affect how the coronavirus evolves – but that’s no reason to skip your shot<figure><img src="https://images.theconversation.com/files/417696/original/file-20210824-14-e2lseo.jpg?ixlib=rb-1.1.0&rect=416%2C0%2C7762%2C5199&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Vaccines against COVID-19 are the safest – and fastest – way to prevent the spread of variants.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-preparing-flu-or-coronavirus-injection-royalty-free-image/1278800490?adppopup=true">Luis Alvarez/ DigitalVision via Getty Images</a></span></figcaption></figure><p><strong>Takeaways</strong></p>
<ul>
<li><p>A 2015 paper on a chicken virus showed vaccines could enable more deadly variants to spread – in chickens.</p></li>
<li><p>But that outcome is rare. Only a minority of human and animal vaccines have affected the evolution of a virus. In most of those cases, evolution didn’t increase the severity of the pathogen.</p></li>
<li><p>The hypothetical possibility that the COVID-19 vaccines could result in more harmful variants is no reason to avoid inoculation. Rather, it shows the need to continue developing vaccines. </p></li>
</ul>
<hr>
<p>In 2015, my collaborators and I published a <a href="https://doi.org/10.1371/journal.pbio.1002198">scientific paper</a> about a chicken virus you have likely never heard of. At the time, it got <a href="https://www.nationalgeographic.com/science/article/leaky-vaccines-enhance-spread-of-deadlier-chicken-viruses">some</a> media attention and has been <a href="https://scholar.google.com/citations?view_op=view_citation&hl=en&user=zFQh3-EAAAAJ&cstart=20&pagesize=80&sortby=pubdate&citation_for_view=zFQh3-EAAAAJ:IaI1MmNe2tcC">cited by other scientists</a> in the years since. </p>
<p>But now, by late-August 2021, the paper <a href="https://journals.plos.org/plosbiology/article/metrics?id=10.1371/journal.pbio.1002198">has been viewed</a> more than 350,000 times – and 70% of those views were in the past three weeks. It has even appeared on a <a href="https://www.youtube.com/watch?v=tiwsv51Il4k&t=52s">YouTube video</a> that’s been seen by 2.8 million people, and counting. </p>
<p>The paper has <a href="https://www.altmetric.com/details/4333559#score">gone viral</a> because <a href="https://www.theepochtimes.com/will-covid-19-vaccines-drive-mutated-variants_3910436.html">some people</a> are using it to stoke paranoia that the COVID-19 vaccines will cause the virus to evolve in the direction of even more severe variants. Doctors have told me that patients are using the paper to justify their decision to not get vaccinated. <a href="https://twitter.com/rourecentenari/status/1428647679463206912">Some</a> <a href="https://climate-science.press/2021/05/18/did-they-forget-to-tell-us-leaky-vaccines-may-trigger-an-arms-race-that-makes-covid-more-dangerous/">pundits</a> are even <a href="https://www.facebook.com/photo.php?fbid=10220062692738356&set=a.10200625587182865&type=3">using it</a> to urge an end to vaccination campaigns in order to prevent the sort of viral evolution we were studying in chickens.</p>
<p>I am receiving emails daily from people worried about getting vaccinated themselves or worried about people rejecting vaccination because of misunderstandings about the paper. </p>
<p>Nothing in our paper remotely justifies an anti-vaccine stance. That misinterpretation – if it causes people to choose not to be vaccinated – will lead to avoidable, and tragic, loss of life. A new study estimates that as of early May 2021, vaccines <a href="https://doi.org/10.1377/hlthaff.2021.00619">had already prevented nearly 140,000 deaths</a> in the U.S. </p>
<p>For over <a href="https://doi.org/10.1038/414751a">20 years</a> <a href="https://scholar.google.com/citations?user=zFQh3-EAAAAJ&hl=en">I’ve been working</a> with <a href="https://doi.org/10.1371/journal.pbio.1001368">collaborators</a> and <a href="https://doi.org/10.1098/rsif.2006.0207">colleagues</a> on how vaccines might affect the evolution of disease-causing organisms like <a href="https://doi.org/10.1111/j.1558-5646.2012.01803.x">viruses</a> and <a href="https://doi.org/10.1371/journal.pbio.1001368">malaria parasites</a>. </p>
<p>Nothing we have discovered or even hypothesized justifies avoiding or withholding vaccines. If anything, <a href="https://theconversation.com/virus-evolution-could-undermine-a-covid-19-vaccine-but-this-can-be-stopped-149234">our work adds to reasons</a> for investigating new vaccine schedules – and for developing second- and third-generation vaccines. </p>
<p>But in the context of the COVID-19 virus, our work does prompt a fair question: Could vaccination cause the emergence of even more harmful variants?</p>
<h2>From chickens to COVID-19</h2>
<p>In the <a href="https://doi.org/10.1371/journal.pbio.1002198">2015 paper</a>, we reported experiments with variants of Marek’s disease virus – the name of the chicken virus we were studying. It is <a href="https://doi.org/10.1038/nrmicro1382">a herpesvirus</a> that causes cancer in domestic chickens. A first-generation vaccine against it <a href="https://doi.org/10.1586/14760584.4.1.77">went into widespread use</a> in poultry in the early 1970s. Today, all commercial chickens and many backyard flocks are vaccinated against Marek’s.</p>
<p>Chickens with Marek’s disease virus became capable of transmitting the virus about 10 days after they get infected. In our lab experiments, we worked with variants of Marek’s disease virus that were so lethal they would kill all unvaccinated birds in 10 days or fewer. So prior to the vaccine, the birds died before they could transmit the lethal variants to other birds. But we found that the first-generation vaccine protected the birds from dying. In other words, the Marek’s-infected chickens lived and were thus able to spread the highly virulent strains to other birds. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Penn State biologist Andrew Read holds chicken at poultry farm" src="https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417701/original/file-20210824-26129-1j4qp66.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Penn State biologist Andrew Read (right) and research assistant Chris Cairns studied Marek’s disease virus in poultry chickens.</span>
<span class="attribution"><span class="source">A Chan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>In the case of COVID-19, it’s becoming increasingly clear that even vaccinated people <a href="https://www.nature.com/articles/d41586-021-02259-2?utm_source=Nature+Briefing&utm_campaign=86c75674aa-briefing-dy-20210820&utm_medium=email&utm_term=0_c9dfd39373-86c75674aa-43257777">can contract and transmit</a> the highly transmissible delta variant. Since viral transmission from vaccinated chickens is what allowed more lethal variants to spread in Marek’s, it’s reasonable to ask whether COVID-19 transmission from vaccinated people could allow more lethal variants to spread.</p>
<h2>Evolution can go in many directions</h2>
<p>As evolutionary ecologist <a href="https://scholar.google.com/citations?user=VkV9_zoAAAAJ&hl=en">David Kennedy</a> and I have <a href="https://theconversation.com/virus-evolution-could-undermine-a-covid-19-vaccine-but-this-can-be-stopped-149234">written about</a> previously, the evolutionary path that the Marek’s disease virus took is one of many that are possible – in rare cases where vaccines drive evolution. </p>
<p>Only a minority of human and animal vaccines <a href="https://doi.org/10.1098/rspb.2016.2562">have influenced</a> pathogen evolution. In nearly all of those cases – which include the hepatitis B virus and bacteria that cause whooping cough and pneumonia – <a href="https://doi.org/10.1073/pnas.1717159115">vaccine efficacy was reduced</a> by new variants. But in contrast to Marek’s, there was no clear evidence that the evolved variants made people sicker.</p>
<p>In nature, we know of course that not all viruses are equally lethal. Biological differences in things like the linkage between disease severity and transmission can cause lethality to increase or decrease. This means that the future of one virus cannot be predicted by simply extrapolating from the past evolution of another. Marek’s and SARS-CoV-2 are very different viruses, with very different vaccines, very different hosts and very different mechanisms by which they sicken and kill. It is impossible to know whether their differences are more important than their similarities.</p>
<p>Evolutionary hypotheticals are important to consider. But up against the hugely beneficial impact of COVID-19 vaccines on reducing <a href="http://dx.doi.org/10.15585/mmwr.mm7034e4">transmission</a> and disease severity – <a href="https://doi.org/10.1056/NEJMoa2108891">even against the delta variant</a> – the possibility of silent spread of more lethal variants among the vaccinated is still no argument against vaccination. </p>
<p>As novel variants of the coronavirus spread in the months and years ahead, it will be vital to work out whether their evolutionary advantage is arising because of reduced disease severity among the vaccinated. Delta, for instance, <a href="https://doi.org/10.1038/d41586-021-02259-2">transmits more effectively</a> from both unvaccinated and vaccinated people than did earlier variants. Extrapolating from our chicken work to argue against vaccination because of the delta variant has no scientific rationale: The delta variant would have become dominant even if everyone refused vaccination.</p>
<h2>But what if?</h2>
<p>If more deadly variants of the coronavirus were to arise, lower vaccination rates would make it easier to identify and contain them because unvaccinated people would suffer more severe infections and higher death rates. But that kind of “solution” would come at considerable cost. In effect, the variants would be found and eliminated by letting people get sick, many of whom would die.</p>
<p>Sacrificing chickens was not the solution the poultry industry adopted for Marek’s disease virus. Instead, more potent vaccines were developed. Those newer vaccines provided <a href="https://doi.org/10.1016/j.prevetmed.2015.04.013">excellent disease control</a>, and no lethal breakthrough variants of Marek’s have emerged in over 20 years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Chickens in poultry house in Maryland" src="https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417700/original/file-20210824-18817-l8hni4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Marek’s disease, a cancer-causing herpesvirus in domestic chickens, took a heavy toll on the poultry industry before vaccines were developed against it.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/broiler-chickens-in-poultry-house-royalty-free-image/159235695?adppopup=true">Edwin Remsberg/The Image Bank via Getty Images</a></span>
</figcaption>
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<p>There are probably ways the available COVID-19 vaccines could be improved in the future to <a href="https://theconversation.com/virus-evolution-could-undermine-a-covid-19-vaccine-but-this-can-be-stopped-149234">better reduce transmission</a>. Booster shots, larger doses or different intervals between doses might help; so too, <a href="https://theconversation.com/a-mix-and-match-approach-to-covid-19-vaccines-could-provide-logistical-and-immunological-benefits-161974">combinations of existing vaccines</a>. Researchers are working hard on these questions. Next-generation vaccines might be even better at blocking transmission. Nasal vaccines, for instance, might effectively curtail transmission because they more specifically target the location of transmissible virus.</p>
<p>As of late August 2021, <a href="https://covid.cdc.gov/covid-data-tracker/#datatracker-home">more than 625,000 Americans have died</a> from a disease that is now largely vaccine-preventable. It is sobering for me to think that some of the next to die might have avoided lifesaving vaccines because people are stoking evolutionary fears extrapolated from our research in chickens. </p>
<p>In the history of human and animal vaccines, there have not been many cases of vaccine-driven evolution. But in every one of them, individuals and populations have <a href="https://doi.org/10.1073/pnas.1717159115">always been better off</a> when vaccinated. At <a href="https://doi.org/10.1016/j.prevetmed.2015.04.013">every point</a> in the 50-year history of vaccination against Marek’s disease, an individual chicken exposed to the virus was healthier if it was vaccinated. Variants may have reduced the benefit of vaccination, but they never eliminated the benefit. Evolution is no reason to avoid vaccination.</p><img src="https://counter.theconversation.com/content/165960/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Read received funding for the chicken work from Institute of General Medical Sciences, National Institutes of Health (R01GM105244) and the UK Biotechnology and Biological Sciences Research Council as part of the joint NSF-NIH-USDA Ecology and Evolution of Infectious Diseases program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of this article.</span></em></p>A 2015 paper on chicken virus evolution is being taken out of context and used to fuel fears about COVID-19 vaccines. Its lead author aims to clarify the science in hopes of saving lives.Andrew Read, Professor of Biology, Entomology and Biotechnology, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1662412021-08-20T12:21:48Z2021-08-20T12:21:48ZImmunocompromised people make up nearly half of COVID-19 breakthrough hospitalizations – an extra vaccine dose may help<figure><img src="https://images.theconversation.com/files/417046/original/file-20210819-27-1m7wgcg.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cancer and organ transplant patients, people with untreated HIV and people with other immunodeficiencies are at high risk of severe COVID-19 infection.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-wearing-mask-to-avoid-infectious-diseases-royalty-free-image/1216044531">burakkarademir/E+ via Getty Images</a></span></figcaption></figure><figure class="align-center ">
<img alt="Green background with white text noting that 44% is the share of hospitalized breakthrough case patients in the US who are immunocompromised" src="https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=321&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=321&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417070/original/file-20210819-21-14sn3wq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=321&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p>The <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-vaccine-dose-certain-immunocompromised">U.S. Food and Drug Administration</a> and <a href="https://www.cdc.gov/vaccines/acip/meetings/slides-2021-08-13.html">Centers for Disease Control and Prevention</a> officially recommended on Aug. 12 and Aug. 13, 2021, respectively, that people who are moderately to severely immunocompromised <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html">receive a third dose of the COVID-19 vaccine</a>. </p>
<p>One reason for this recommendation is high hospitalization rates among immunocompromised people who are vaccinated. As of July 2021, <a href="https://www.cdc.gov/media/releases/2021/s0813-additional-mRNA-mrna-dose.html">nearly half of the vaccinated people hospitalized</a> with breakthrough COVID-19 infections were immunocompromised – despite making up only 2.7% of the U.S. adult population. In comparison, the <a href="https://www.kff.org/policy-watch/covid-19-vaccine-breakthrough-cases-data-from-the-states/">rate of breakthrough cases among vaccinated people who are not immunocompromised was less than 1%</a>.</p>
<p>I am a <a href="https://medicine.umich.edu/dept/immunology/jonathan-golob-md-phd">physician scientist specializing in infections in immunocompromised patients</a>. As someone who researches autoimmune disease and has worked on the COVID-19 vaccine trials, I agree that a third dose of COVID-19 vaccine can help protect those with weakened immune systems.</p>
<h2>What does it mean to be immunocompromised?</h2>
<p>People who are immunocompromised have <a href="https://www.hopkinsmedicine.org/health/conditions-and-diseases/disorders-of-the-immune-system">weakened immune systems</a>. This can result from certain diseases and their medical treatments, such as cancer, autoimmune diseases, untreated HIV, organ transplant medications and some forms of kidney disease. The common thread is that the body’s defenses against infection are impaired. </p>
<p>Two parts of the immune system seem to be particularly important in protecting people from getting sick with COVID-19: <a href="https://theconversation.com/coronavirus-b-cells-and-t-cells-explained-141888">T cells and B cells</a>. <a href="https://www.verywellhealth.com/b-cells-2252132">B cells make antibodies</a> that can bind to and inactivate viruses. <a href="https://www.verywellhealth.com/t-cells-2252171">T cells kill off virus-infected cells</a>, prevent infection from further spreading and organize the body’s overall defense response. Different types of immunocompromising conditions and treatments can either <a href="https://medlineplus.gov/ency/article/000818.htm">kill or decrease the effectiveness</a> of these key immune cells.</p>
<p>That can result in a <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html">hampered response</a> to vaccines. As a result, people who are immunocompromised often need to <a href="https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/immunocompetence.html">follow different vaccination guidelines</a> from people who are not immunocompromised to best protect themselves from infection. After a bone marrow or solid organ transplant, for instance, patients are <a href="https://doi.org/10.1016/j.clinthera.2017.07.005">routinely revaccinated against such infections</a> as hepatitis B. </p>
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<h2>COVID-19 is particularly dangerous for the immunocompromised</h2>
<p>Early on in the pandemic, researchers learned that immunocompromised people infected with COVID-19 tend to have <a href="https://dx.doi.org/10.1093%2Fcid%2Fciaa863">particularly severe and long-lasting infections</a>. This leads to <a href="https://theconversation.com/whats-the-difference-between-viral-shedding-and-reinfection-with-covid-19-150547">prolonged viral shedding</a>, meaning that the period during which these infected people release the virus as they breathe, talk and eat is much longer. Thus, they have a higher chance of transmitting the virus to others.</p>
<p>Long infections with poor immune responses are also <a href="https://www.vox.com/science-and-health/22586816/next-coronavirus-variant-delta-covid-19">ideal environments for the virus to evolve and adapt</a> in ways that allow it to better infect people.</p>
<p>While immunocompromised people <a href="https://doi.org/10.1172/jci.insight.149187">were not included in the initial COVID-19 vaccine trials</a> to avoid putting them at risk, <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html">subsequent studies</a> revealed that the authorized two-dose mRNA vaccine regimens do not stimulate as strong a defense against COVID-19 for immunocompromised people. In particular, <a href="https://doi.org/10.1001/jama.2021.7489">organ transplant recipients</a> seem to develop fewer COVID-19 antibodies after vaccination. That’s not surprising, given that the medicines used in transplantation <a href="https://pubmed.ncbi.nlm.nih.gov/25734416/">intentionally hamper antibody development</a> to prevent the immune system from rejecting the donated organs. But since then, <a href="https://doi.org/10.1056/NEJMc2111462">pilot trials in organ transplant recipients</a> have shown that an additional dose of vaccine can help boost immune response.</p>
<p>The best protection for everyone against COVID-19 is to have <a href="https://www.nytimes.com/2020/10/04/opinion/coronavirus-vaccines-masks.html">as many people vaccinated</a> as soon as possible. In the interim, a third vaccine dose can <a href="https://doi.org/10.1056/NEJMc2108861">safely and effectively</a> decrease the likelihood of severe COVID-19 in immunocompromised people. And <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/about-face-coverings.html">consistently wearing masks</a>, regardless of vaccination status and whether or not you’re immunocompromised, can also significantly reduce the spread of COVID-19.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/166241/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Golob does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>People with weakened immune systems are at a high risk of severe and prolonged COVID-19 infections. An extra vaccine dose can bolster protection.Jonathan Golob, Assistant Professor of Infectious Disease, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1660392021-08-12T13:59:04Z2021-08-12T13:59:04ZCOVID vaccine weekly: do British teenagers really need vaccinating more than adults overseas?<figure><img src="https://images.theconversation.com/files/415854/original/file-20210812-17-x3yyg9.jpg?ixlib=rb-1.1.0&rect=264%2C293%2C4487%2C2702&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/group-teenage-students-uniform-outside-school-779645431">Monkey Business Images/Shutterstock</a></span></figcaption></figure><p>Close to <a href="https://ourworldindata.org/covid-vaccinations">40 million people</a> in the UK have had two COVID vaccine doses. This gives Britain one of the <a href="https://ourworldindata.org/covid-vaccinations">highest rates of coverage</a> in the world, with nearly 60% of the population fully vaccinated. And with vaccines soon to be rolled out to 16- and 17-year-olds, this is going to increase further still.</p>
<p>Expanding vaccination into younger age groups has an array of benefits, <a href="https://theconversation.com/vaccinating-teenagers-is-beneficial-even-if-their-vulnerability-to-covid-19-is-low-165690">says</a> Alex Richter, professor and honorary consultant in clinical immunology at the University of Birmingham. Although severe disease is rare in young people, long COVID is a problem, and allowing the virus to move unchecked through young people disrupts their and their loved ones’ lives. Vaccinating younger people also lessens the risk that they’ll pass the virus on to elderly relatives, who may be vulnerable despite being vaccinated. </p>
<p>But despite these benefits, some – including the <a href="https://www.theguardian.com/world/2021/may/14/vaccinate-vulnerable-global-poor-before-rich-children-who-says">World Health Organization</a> – argue that these vaccines would be better given to vulnerable people in countries where coverage is low, as this is where they would have the greatest impact. The WHO has made a similar argument regarding vaccine boosters: that rich countries shouldn’t be offering some people a third dose – even if they are vulnerable – when many elsewhere are yet to receive a first. </p>
<p>Nevertheless, the UK government seems to be set on prioritising its domestic vaccination programme. This is despite there being a “powerful altruistic argument” behind the WHO’s stance, as Jonathan Pugh, Dominic Wilkinson and Julian Savulescu at the University of Oxford <a href="https://theconversation.com/covid-who-calls-for-moratorium-on-booster-shots-is-it-justifiable-165762">have argued</a>.</p>
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<img alt="" src="https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/320716/original/file-20200316-18073-ruhw8b.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><strong>This is our weekly round-up of expert information about the <a href="https://theconversation.com/uk/topics/covid-vaccines-96571">COVID-19 vaccines</a>.</strong> <br>
The Conversation, a not-for-profit group, works with a wide range of academics across its global network to produce evidence-based analysis and insights. Get more regular updates from trusted experts by <a href="https://theconversation.com/uk/newsletters/the-daily-2">subscribing to our free newsletter</a> .</em></p>
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<p>If Britain’s booster programme does go ahead, one group that <a href="https://inews.co.uk/news/health/covid-booster-vaccine-when-get-who-3rd-jab-roll-out-shot-vaccination-start-1135560">may be prioritised</a> are those with weakened immune systems. We’re still building a picture of how effective COVID vaccines are in this group, but a growing body of evidence shows that vaccines work less well in the immunocompromised, <a href="https://theconversation.com/how-will-covid-vaccines-work-on-compromised-immune-systems-heres-what-we-know-164107">writes</a> Steven Smith, a senior lecturer in biomedical sciences at Brunel University. Hence the need for a top-up. </p>
<p>What makes things more complicated is that immunocompromised people are not a uniform group. There are many reasons why someone may have poor immune function, and the varying reasons behind this appear to affect vaccine performance. Some immunocompromised people may really benefit from a booster dose – but some appear not to respond to COVID vaccines at all.</p>
<p>Thanks to the increased transmissibility of the delta variant, experts have <a href="https://www.theguardian.com/world/2021/aug/10/delta-variant-renders-herd-immunity-from-covid-mythical">declared</a> that vaccine-induced herd immunity is probably now out of sight. This is a blow, but in the UK we should keep in mind that it’s a privilege that we’re even considering herd immunity. In Africa, for instance, limited vaccine supplies, distribution difficulties and hesitancy mean that achieving the sort of coverage needed for population-wide protection is way off, <a href="https://theconversation.com/why-population-immunity-is-not-a-realistic-goal-in-africas-bid-to-control-covid-19-165700">write</a> Edina Amponsah-Dacosta and Benjamin Kagina of the University of Cape Town. </p>
<p>Would making vaccines mandatory help? Possibly a little bit. In South Africa, enforcing uptake among everyone who is medically able would save lives, use limited resources efficiently, and build social cohesion and public trust in vaccines, <a href="https://theconversation.com/why-covid-19-vaccines-should-be-mandatory-in-south-africa-165682">argues</a> Keymanthri Moodley, director of the Centre for Medical Ethics and Law at Stellenbosch University. Not only that, but South Africa has the laws and constitutional rules in place that would allow for such a policy. </p>
<p>But even if this were to solve the issues of hesitancy and distribution, the question of limited resources remains. This returns us to the question of whether countries such as the UK – with their plans for boosters and adolescent vaccine programmes – are doing what’s best for the world with their supplies.</p>
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<p><em>Get the latest news and advice on <a href="https://theconversation.com/uk/covid-19">COVID-19</a>, direct from the experts in your inbox. Join hundreds of thousands who trust experts by <strong><a href="https://theconversation.com/uk/newsletters/the-daily-2">subscribing to our newsletter</a></strong>.</em></p><img src="https://counter.theconversation.com/content/166039/count.gif" alt="The Conversation" width="1" height="1" />
Getting first doses to countries short of supplies should be the priority, argues the World Health Organization.Rob Reddick, Commissioning Editor, COVID-19Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1641252021-07-09T11:17:28Z2021-07-09T11:17:28ZCOVID-19 vaccine boosters: is a third dose really needed?<p>The UK is enjoying real success with its COVID-19 vaccine coverage. Around 85% of adults (44.8 million people) have received one vaccine dose and 63% (33 million people) both doses, with around 160,000 doses a day <a href="https://www.bbc.co.uk/news/health-55274833">still being administered</a>.</p>
<p>Vaccination with two doses helps prevent infection, and in those that do still get infected, <a href="https://pubmed.ncbi.nlm.nih.gov/33964222/">lessens the impact</a> of the virus by reducing disease severity, transmission of infection and death. </p>
<p>Even so, plans to give people a third shot <a href="https://www.gov.uk/government/publications/jcvi-interim-advice-on-a-potential-coronavirus-covid-19-booster-vaccine-programme-for-winter-2021-to-2022/jcvi-interim-advice-potential-covid-19-booster-vaccine-programme-winter-2021-to-2022#fnref:1">have been unveiled</a> by the UK’s Joint Committee on Vaccination and Immunisation (JCVI). The two main arguments to support giving a third dose are that the effectiveness of the first two jabs falls over time, and that there’s a need to take new vaccines to deal with viral variants, such as the delta variant. But what does the evidence say?</p>
<p>Several studies have investigated the durability of immunity to COVID-19, and their results are encouraging. Researchers have focused on specialised white blood cells called lymphocytes. Lymphocytes come in <a href="https://theconversation.com/coronavirus-b-cells-and-t-cells-explained-141888">two main varieties</a>: B cells, which make antibodies, and T cells, which can help the B-cell response or directly kill the COVID-19 virus.</p>
<p>Antibodies play a critical role in stopping viruses entering the body’s cells, which is what the virus needs to do to replicate. You can readily measure someone’s antibody levels in a blood sample, but the data on what a typical person’s antibody levels are following vaccination or infection with COVID-19 has been variable.</p>
<p>Most people have good persistent levels of antibodies that can be detected for <a href="https://www.sciencedirect.com/science/article/abs/pii/S1074761320304453">at least seven months</a>. However, some other people have quite low levels of antibodies or their levels <a href="https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00025-2/fulltext">rapidly fall</a> after infection or vaccination. Such variability makes it difficult to know how useful antibody data alone is for measuring lasting immunity to infection.</p>
<p>A clearer picture can emerge if other indicators of immunity are considered: our B and T cells. A <a href="https://www.researchsquare.com/article/rs-612205/v1">recent preprint</a> (a piece of research still awaiting review by other scientists) suggests that looking at both antibodies and T cells gives a clearer picture of whether immunity has lasted. </p>
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<img alt="An illustration of T cells" src="https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410545/original/file-20210709-13-1n2wj7m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">T cells also form part of the immune response against COVID-19, along with antibodies.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-illustration-lymphocytes-t-cells-cancer-1109342633">Design_Cells/Shutterstock</a></span>
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<p>And reassuringly, functional T-cell responses against COVID-19 have been detected <a href="https://www.nature.com/articles/s41590-021-00902-8">six months after infection</a>. Similarly, <a href="https://theconversation.com/covid-19-immunity-how-long-does-it-last-152849">memory B cells</a> – long-lasting cells kept on hand in case the immune system encounters COVID-19 in the future – <a href="https://www.biorxiv.org/content/10.1101/2021.05.30.446322v1">have been detected</a> in people even when their antibody levels have fallen so low as to be undetectable (though this research is also still waiting review). This suggests that even after their antibodies have waned over time, these people have the means to quickly produce new ones should they face the coronavirus again.</p>
<p>Older people (>80years) often have less effective immune responses when infected or vaccinated, meaning their overall immunity may be lower and may fade more quickly. In any booster campaign they would be likely to be prioritised. However, so far the data for older people has been encouraging. Another <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3816840">recent preprint</a> has shown that older people produce a strong immune response following vaccination.</p>
<p>All these studies are immensely reassuring. Added to what we know about <a href="https://www.sciencedirect.com/science/article/pii/S0966842X21000925">immune responses to viruses</a> more widely, there’s growing confidence that immunity to COVID-19 is durable – although longer-term studies will still be needed. Nevertheless, right now there isn’t strong evidence that people’s immunity needs topping up with a booster.</p>
<h2>Can current vaccines handle variants?</h2>
<p>There are now several variants of the coronavirus in circulation, with four to date – alpha, beta, gamma and delta – being deemed <a href="https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/">variants of concern</a> (VOCs). These are variants that spread more easily, cause worse disease or are less well managed by vaccines.</p>
<p>Initial studies on the effectiveness of vaccines against the alpha variant – one of the first discovered – <a href="https://science.sciencemag.org/content/371/6534/1152">have been encouraging</a>. And while early data on the gamma variant suggested it may be somewhat able to evade <a href="https://www.bmj.com/content/373/bmj.n1353">immunity</a>, a subsequent preprint suggests that vaccines still <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3816840">protect against it</a>. </p>
<p>There have been concerns too about the delta variant, however <a href="https://khub.net/web/phe-national/public-library/-/document_library/v2WsRK3ZlEig/view_file/479607329?_com_liferay_document_library_web_portlet_DLPortlet_INSTANCE_v2WsRK3ZlEig_redirect=https%3A%2F%2Fkhub.net%3A443%2Fweb%2Fphe-national%2Fpublic-library%2F-%2Fdocument_library%2Fv2WsRK3ZlEig%2Fview%2F479607266">data from Public Health England</a> (also still in preprint) suggests vaccines offer robust protection against it. Even when vaccines give reduced protection – <a href="https://pubmed.ncbi.nlm.nih.gov/33725432/">as seen with the beta variant</a> – more <a href="https://www.medrxiv.org/content/10.1101/2021.06.28.21259420v1.full.pdf">early research</a> (again awaiting review) suggests they still protect against the worst impacts of disease. </p>
<p>The evidence is showing vaccination is working: immunity is lasting and is protecting us against the worst effects of COVID-19. So why is the UK planning on third booster shots when there isn’t clear evidence that there’s a need? A huge concern should be that the majority of people in the world still remain unvaccinated. In many low-income countries as little as 1% of <a href="https://ourworldindata.org/covid-vaccinations">eligible adults</a> have received one vaccine dose. </p>
<p>Poor vaccine coverage enables the virus to thrive. When it infects and reproduces in many thousands of people, this gives the virus <a href="https://theconversation.com/why-more-contagious-variants-are-emerging-now-more-than-a-year-into-the-covid-19-pandemic-155302">an opportunity to mutate</a>, which can lead to new variants emerging. It’s no coincidence that the VOCs all emerged from areas with high levels of viral transmission. There are also at least seven <a href="https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/">variants of interest</a> that have also emerged from areas with high levels of viral transmission. These are viruses with the potential to be VOCs, and so are being monitored to see what threats they could pose.</p>
<p>To prevent more VOCs appearing, we urgently need to get ahead of the virus – not just in the UK, but everywhere. The evidence to date doesn’t suggest there’s an urgent need to give people a third COVID-19 vaccine dose in rich countries like the UK. It would be better to give those doses to countries with low coverage, rather than launching a booster programme. Because until we have high vaccine coverage around the world, we can never truly hope to escape this pandemic.</p><img src="https://counter.theconversation.com/content/164125/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sheena Cruickshank does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If immunity is waning or ineffectual against new variants, then boosters could be needed – but there needs to be evidence that they’re necessary.Sheena Cruickshank, Professor in Biomedical Sciences, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1641642021-07-09T05:49:03Z2021-07-09T05:49:03ZShould I have my AstraZeneca booster shot at 8 weeks rather than 12? Here’s the evidence so you can decide<figure><img src="https://images.theconversation.com/files/410496/original/file-20210709-19-eimpsf.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C519&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-top-view-on-white-calendar-1861762180">from www.shutterstock.com</a></span></figcaption></figure><p>Prime Minister Scott Morrison appeared to have made a “captain’s call” yesterday by <a href="https://www.abc.net.au/news/2021-07-08/scott-morrison-covid-vaccine-nsw-outbreak/100277466">encouraging people</a> in New South Wales outbreak areas to have their AstraZeneca booster closer to eight weeks after their initial shot rather than wait for the generally recommended 12 weeks.</p>
<blockquote>
<p>We would be encouraging the eight to 12-week second dose be done at the earlier part of that period […]. That is consistent with medical advice […] and given the risks to people from the outbreak in that area we believe it is important they get that second dose of AstraZeneca as soon as possible.</p>
</blockquote>
<p>The official health advice from ATAGI, the Australian Technical Advisory Group on Immunisation, remains most people have their booster shot <a href="https://www.health.gov.au/sites/default/files/documents/2021/06/covid-19-vaccination-atagi-clinical-guidance-on-covid-19-vaccine-in-australia-in-2021_1.pdf">at 12 weeks</a> for optimal COVID protection, but under certain circumstances that can go down to four weeks. Those circumstances include imminent travel or if there’s a risk of COVID-19 exposure.</p>
<p>ATAGI’s concern, and that of <a href="https://www.smh.com.au/national/vaccine-experts-warn-against-reducing-time-between-astrazeneca-doses-20210707-p587n6.html">some other vaccine experts</a>, is if you have your booster shot earlier than 12 weeks, your body won’t develop enough immunity to reliably protect you from serious disease.</p>
<p>Confused? Here is what we know so far.</p>
<h2>What’s the official advice?</h2>
<p>The evidence underpinning the <a href="https://www.health.gov.au/sites/default/files/documents/2021/06/covid-19-vaccination-atagi-clinical-guidance-on-covid-19-vaccine-in-australia-in-2021_1.pdf">recommended 12 week gap</a> between the first and second AstraZeneca shots comes from a study published in <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00432-3/fulltext">the Lancet</a>. </p>
<p>The study found leaving less than six weeks between the initial shot and the booster gave 55.1% efficacy (protection from symptomatic disease). Leaving 6-8 weeks between shots increased efficacy to 59.9%, and waiting 9-11 weeks, efficacy was 63.7%. However, if the gap was 12 weeks or longer efficacy jumped to 81.3%.</p>
<p>So to get the best protection from the AstraZeneca vaccine, you need at least 12 weeks between your first and second shot.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408593/original/file-20210628-27-1lcjcwa.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
<span class="attribution"><a class="source" href="https://www.sciencedirect.com/science/article/pii/B978032335761600002X">The Conversation (adapted from Vaccine Immunology, Plotkin's Vaccines [Seventh Edition] 2018)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Now we find ourselves with an active outbreak of the highly transmissible Delta variant of SARS-CoV-2 in Sydney. So we need to ask ourselves whether aiming for the highest level of protection is best, or whether we need to aim for a reasonable level of immunity as quickly as possible.</p>
<p>The Lancet paper didn’t include data on the Delta variant as it wasn’t widely circulating at the time, but this is fast becoming the <a href="https://www.euronews.com/2021/06/23/delta-variant-to-account-for-90-of-new-covid-19-cases-in-europe-by-late-august-warns-eu-ag">dominant variant globally</a>.</p>
<p>Yet we do know <a href="https://theconversation.com/should-i-get-my-second-astrazeneca-dose-yes-it-almost-doubles-your-protection-against-delta-163259">two doses</a> of the AstraZeneca vaccine protects against serious COVID-19 after infection with the Delta variant, whereas <a href="https://www.nature.com/articles/s41586-021-03777-9">one dose doesn’t</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/should-i-get-my-second-astrazeneca-dose-yes-it-almost-doubles-your-protection-against-delta-163259">Should I get my second AstraZeneca dose? Yes, it almost doubles your protection against Delta</a>
</strong>
</em>
</p>
<hr>
<h2>What’s the evidence for 8 weeks to protect against Delta?</h2>
<p>Morrison’s call for some people to have their AstraZeneca booster shot from around eight weeks hasn’t come completely out of the blue. It’s an approach <a href="https://www.health-ni.gov.uk/news/introduction-shorter-interval-between-vaccine-doses">the UK has been using</a> to get ahead of the infectious Delta variant, the same variant circulating in NSW.</p>
<p>We know leaving less time between AstraZeneca shots generally reduces vaccine efficacy. But what about that in the context of the Delta variant? This is where things get a bit tricky if we actually want to put a figure on precisely how much vaccine efficacy reduces.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1412989844511285250"}"></div></p>
<p>A study published in <a href="https://www.nature.com/articles/s41586-021-03777-9">Nature</a> reported a single dose of AstraZeneca vaccine induced essentially no Delta virus-neutralising antibodies. </p>
<p>However, two doses induced a neutralising antibody response in 95% of people, albeit at a significantly lower level than with the Alpha variant (which originated in the UK).</p>
<p>Still, neutralising antibodies against Delta were there in the vast majority of people after two shots, antibodies that could mean the difference between a mild illness and hospitalisation with severe disease. </p>
<p>There are some limitations with this study. First, it did not directly assess vaccine efficacy (you need to conduct a clinical trial for that). Second, it used a range of intervals between first and second shots, so we cannot definitively say the precise protection from the Delta strain at eight weeks versus 12 weeks. </p>
<p>However, assessing the capacity of vaccinated peoples’ antibodies to neutralise viruses in the lab is a good indicator of the quality of vaccine-induced protection — and this study really highlighted the need for a booster shot for protection against the Delta variant. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-symptoms-of-the-delta-variant-appear-to-differ-from-traditional-covid-symptoms-heres-what-to-look-out-for-163487">The symptoms of the Delta variant appear to differ from traditional COVID symptoms. Here's what to look out for</a>
</strong>
</em>
</p>
<hr>
<p>So with infection numbers in Sydney looking more ominous by the day, coupled with the knowledge one vaccine dose is all but useless against the Delta virus, it is clear getting two doses into the arms of as many people as possible as quickly as possible, is the strategy. </p>
<p>Two doses, even at eight weeks apart, while not providing the highest possible level of protection, will still protect many from severe disease. </p>
<h2>What else do I need to think about?</h2>
<p>A drop in immunity is not the only thing to consider when weighing up the pros and cons of having your AstraZeneca booster shot early.</p>
<p>We’ve just heard more Pfizer shots are on their way <a href="https://www.abc.net.au/news/2021-07-09/australia-to-get-pfizer-covid19-vaccine-supply-august/100279944">sooner than expected</a>. If a Pfizer booster shot is made available to people who have already had two shots of AstraZeneca (and this is a big if), this could be a game changer.</p>
<p>In this case — and remember this mix-and-match approach has not been officially sanctioned — it might not matter too much if an early second dose of the AstraZeneca vaccine gives you sub-optimal immunity. The Pfizer booster would lift your immunity instead. </p>
<p>However, it remains to be seen whether such a major policy shift would happen in time to protect people currently in lockdown in NSW.</p>
<h2>Take-home message</h2>
<p>The Delta variant is <a href="https://theconversation.com/why-is-delta-such-a-worry-its-more-infectious-probably-causes-more-severe-disease-and-challenges-our-vaccines-163579">highly transmissible</a>. So weeks do matter, and with Australia still heavily reliant on the AstraZeneca vaccine, for now it does makes sense to reduce the time between the first and second jab. </p>
<p>This is clearly preferable to remaining unprotected for an extra month, particularly if you are at higher risk of infection and/or severe disease.</p><img src="https://counter.theconversation.com/content/164164/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Bartlett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Weeks do matter when it comes to the Delta strain. With Australia still heavily reliant on the AstraZeneca vaccine, for now it makes sense to reduce the time between the first and second jab.Nathan Bartlett, Associate Professor, School of Biomedical Sciences and Pharmacy, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1640532021-07-08T12:36:37Z2021-07-08T12:36:37ZDo I need a COVID-19 booster shot? 6 questions answered on how to stay protected<figure><img src="https://images.theconversation.com/files/410015/original/file-20210706-25-16rvtbn.jpg?ixlib=rb-1.1.0&rect=21%2C5%2C3573%2C4489&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A booster shot may be necessary to maintain COVID-19 immunity.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/mAGZNECMcUg">Daniel Schludi/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>The increasing prevalence of <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/variant.html">new coronavirus variants</a> is raising questions about how well protected those who’ve already had their COVID-19 shots are against evolving forms of the SARS-CoV-2 virus. Here, <a href="https://scholar.google.com/citations?user=6yMIM1MAAAAJ&hl=en&oi=ao">microbiology and infectious disease specialist William Petri</a> of the University of Virginia answers some common questions about COVID-19 booster shots.</em></p>
<h2>1. What is a booster shot?</h2>
<p>Boosters are an extra dose of a vaccine given to maintain vaccine-induced protection against a disease. They are commonly used to bolster many vaccines because immunity can <a href="https://doi.org/10.1038/s41577-020-00479-7">wear off over time</a>. For example, the <a href="https://www.cdc.gov/vaccines/parents/diseases/flu.html">flu vaccine</a> needs a booster every year, and the <a href="https://www.cdc.gov/vaccines/vpd/dtap-tdap-td/hcp/recommendations.html">diphtheria and tetanus vaccine</a> every 10 years. </p>
<p>Boosters are often identical to the original vaccine. In some cases, however, the booster shot has been modified to enhance protection against new viral variants. The <a href="https://www.cdc.gov/flu/prevent/keyfacts.htm">seasonal flu vaccine</a>, most notably, requires an annual booster because the flu virus changes so rapidly.</p>
<h2>2. Do I need to get a COVID-19 booster?</h2>
<p>Only if you’re immunocompromised. As of August 2021, the <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-vaccine-dose-certain-immunocompromised">U.S Food and Drug Administration</a> and <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html">Centers for Disease Control and Prevention</a> recommend adding a third shot to the normal vaccination course for people who are severely immunocompromised.</p>
<h2>3. Why aren’t booster shots recommended for everyone yet?</h2>
<p>While vaccine-induced immunity may not last forever, it is not clear when a booster will be needed. </p>
<p>Encouragingly, all of the currently authorized COVID-19 vaccines induce a robust immune memory against the coronavirus. The vaccine teaches your immune system’s <a href="https://doi.org/10.3389/fimmu.2019.01787">memory B cells</a> to produce antibodies when you’re exposed to the virus. Researchers have detected high levels of memory B cells in the lymph nodes of people who received the Pfizer vaccine for <a href="https://doi.org/10.1038/s41586-021-03738-2">at least 12 weeks</a> after they got the shot.</p>
<p>Studies also suggest that authorized COVID-19 vaccines are continuing to offer protection even against <a href="https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/">emerging strains of the coronavirus</a>. Among one study’s participants, the Johnson & Johnson vaccine had <a href="https://doi.org/10.1056/NEJMoa2101544">73% and 82% efficacy</a> 14 days and 28 days post shot, respectively, at warding off severe disease from the beta variant. Another study found the Pfizer vaccine to be <a href="https://doi.org/10.1056/NEJMoa2108891">88% effective</a> against the delta variant.</p>
<p>The other source of long-lasting antibody responses against the coronavirus is cells called <a href="https://doi.org/10.3389/fimmu.2019.01787">plasmablasts</a> that reside in bone marrow. These cells continuously produce antibodies and do not require boosting to maintain their activity. Fortunately, plasmablasts have been detected in the bone marrow of <a href="https://doi.org/10.1038/s41586-021-03647-4">people who received the COVID-19 vaccine</a> for up to 11 months, indicating some degree of long-lasting immune memory.</p>
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<figcaption><span class="caption">Booster shots remind your immune system of the pathogen it’s been immunized against.</span></figcaption>
</figure>
<h2>4. How will I know if I need a booster?</h2>
<p>You may need to wait for an outbreak in people who have been vaccinated. Researchers are still figuring out the best way to measure the strength of someone’s vaccine-induced immunity. The COVID-19 vaccines have been so effective that there are not many failures to test. </p>
<p>The best candidate to measure are certain antibodies the vaccine induces the immune system to make. They recognize the <a href="https://doi.org/10.1056/NEJMoa2034577">spike protein</a> that allows the coronavirus to enter and infect cells. Evidence supporting the importance of anti-spike antibodies includes a study showing that the somewhat more effective mRNA vaccines like Pfizer and Moderna generate <a href="https://doi.org/10.1016/j.vaccine.2021.05.063">higher antibody levels in the blood</a> than the adenovirus vector vaccines like Johnson & Johnson and AstraZeneca. In a <a href="https://doi.org/10.1101/2021.06.21.21258528">preliminary study</a> that has not yet been peer-reviewed, anti-spike antibody levels were lower in people who caught COVID-19 after they were vaccinated with the Oxford–AstraZeneca vaccine.</p>
<p>Medical workers would love to be able to give patients a blood test that would tell them how well protected they are or aren’t against COVID-19. That would be a clear indication as to whether a booster shot is needed.</p>
<p>But until researchers know for sure how to measure vaccine-induced immunity, the next indication that boosters may be needed are breakthrough infections in older adults who have already been vaccinated. People over the age of 80 make <a href="https://doi.org/10.1038/s41586-021-03739-1">lower levels of antibodies</a> after vaccination, so their immunity may wane sooner than that of the general population. The elderly would also most likely be the <a href="https://doi.org/10.1038/s41586-021-03739-1">most susceptible to new viral variants</a> that evade the protection current vaccines provide.</p>
<h2>5. Who does the FDA and CDC recommend get a third shot?</h2>
<p>An extra shot may be necessary for certain immunocompromised people. In one study, 39 of 40 kidney transplant recipients and a third of dialysis patients <a href="https://doi.org/10.1126/sciimmunol.abj1031">failed to make antibodies after vaccination</a>. Another study identified 20 patients with <a href="https://doi.org/10.7326/M21-1451">rheumatic or musculoskeletal diseases</a> on medications that suppress the immune system who also did not have detectable antibodies. Both of these studies were done after patients received the full vaccine dose.</p>
<p>Currently, the CDC recommends that <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html/">the following people consider getting a third dose</a>:</p>
<ul>
<li>People in active cancer treatment</li>
<li>People who have received organ transplants and are taking immunosuppressive therapy</li>
<li>People who have received a stem cell transplant within the past two years or are taking immunosuppressive therapy</li>
<li>People with moderate or severe primary immunodeficiency</li>
<li>People with advanced or untreated HIV infection</li>
<li>People taking high-dose corticosteroids and other immunosuppressive drugs</li>
</ul>
<p>A third dose has been shown to help in these cases. In one study, one-third of <a href="https://doi.org/10.7326/L21-0282">solid organ transplant patients</a> who had a suboptimal response to two doses of the Pfizer or Moderna vaccines were able to develop an antibody response with a third dose. </p>
<p>Those who are immunocompromised may wonder if the vaccine they received is successfully generating immunity in their body. A preliminary study that has not yet been peer-reviewed did find that a <a href="https://doi.org/10.1101/2021.03.05.21252977">test that specifically targets the anti-spike antibodies</a> the vaccines trigger may be helpful in determining whether the vaccine worked. But for now, the <a href="https://www.fda.gov/medical-devices/safety-communications/antibody-testing-not-currently-recommended-assess-immunity-after-covid-19-vaccination-fda-safety">FDA does not recommend</a> antibody tests to assess immunity.</p>
<h2>6. Does my third dose need to match my first two?</h2>
<p>Likely not. Recent research has shown that mRNA vaccines, like Pfizer and Moderna, can be mixed with adenovirus-based vaccines like AstraZeneca with <a href="http://dx.doi.org/10.2139/ssrn.3874014">comparable results</a>.</p>
<p><em>Article corrected to indicate that the Johnson & Johnson study measured efficacy rather than effectiveness against severe disease from the beta variant of the virus that causes COVID-19.</em></p>
<p><em>Article updated to reflect FDA authorization and CDC recommendation of an additional dose for immunocompromised individuals on Aug. 12, 2021, and Aug. 13, 2021, respectively.</em></p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/164053/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Petri receives funding from NIH, the Bill & Melinda Gates Foundation, and Regeneron, Inc.</span></em></p>Though currently approved COVID-19 vaccines effectively provide immunity against the virus, it’s unclear how long that protection will last.William Petri, Professor of Medicine, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1608882021-05-18T12:25:01Z2021-05-18T12:25:01ZUK vaccine booster Q&A: what will be given and when, explained by public health expert<figure><img src="https://images.theconversation.com/files/401242/original/file-20210518-17-q93hee.jpg?ixlib=rb-1.1.0&rect=32%2C123%2C5292%2C3273&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/elderly-man-getting-coronavirus-vaccine-1893080998">Melinda Nagy/Shutterstock</a></span></figcaption></figure><p>The national effort to immunise the UK population against COVID-19 has been phenomenal. In six months, more than <a href="https://coronavirus.data.gov.uk/details/vaccinations">56 million vaccine doses</a> have been given to over 36 million people. With the distribution of first and second doses going well, the British government is now considering if and when it should give people a third, booster dose.</p>
<p>However, <a href="https://www.bbc.co.uk/news/live/uk-56991714">reports</a> so far have been <a href="https://metro.co.uk/2021/05/08/uk-will-be-covid-free-by-august-and-booster-jabs-can-be-pushed-back-14543145/">contradictory</a>. They’ve offered <a href="https://www.thetimes.co.uk/article/third-covid-vaccine-for-over-50s-before-winter-jhpj57g0d">different suggestions</a> on when boosters will be given, who they’ll be given to, and what exactly people might receive. But while it’s impossible to say for sure what will happen in the future, based on what we know about COVID-19 and the pandemic, it is possible to predict broadly how a booster programme could operate.</p>
<p>Undoubtedly, there’s a desire to end lockdown restrictions, reopen the country and keep it open – and this is why a third vaccine dose is being considered. Reopening safely will require two key conditions to be met: firstly, that most people get vaccinated, and secondly, that the vaccines remain effective. Boosters may be needed to ensure the latter. Here’s how they might work.</p>
<h2>Who will be offered a third vaccine?</h2>
<p>People whose earlier vaccine protection may have worn off are likely to be prioritised.</p>
<p>Currently, it’s not certain how long COVID-19 vaccine protection lasts, though studies suggest <a href="https://www.nejm.org/doi/10.1056/NEJMc2103916">at least six months</a>. However, vaccine protection varies by individual and naturally wanes over time. For some people, this waning happens more rapidly, for <a href="https://www.immunology.org/sites/default/files/BSI_Briefing_Note_2021_immunity_COVID19.pdf">reasons</a> such as old age, the effect of some chronic illness, or taking treatments that may suppress the immune system. </p>
<p>Consequently, a booster dose is likely to be needed for people in these high-risk groups to make sure good immune protection is maintained. Indeed, the UK’s Department of Health and Social Care has said that boosters will be distributed <a href="https://www.bmj.com/content/373/bmj.n1116?ijkey=44035bce6459ec0384787104b692612c0ab153cc&keytype2=tf_ipsecsha">based on clinical need</a>. </p>
<h2>When might boosters start being given?</h2>
<p>Ahead of when future waves of infection are anticipated. Epidemics of human coronaviruses are usually <a href="https://academic.oup.com/jid/article/222/1/17/5820656?login=true">seasonal in nature</a>, typically occurring in the winter months. Thus, the ideal timing for the vaccine booster programme will be in the autumn months so that most of the vulnerable population is protected in time for any winter outbreaks.</p>
<p>Current efforts are targeted at immunising the UK adult population with two doses <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/951928/uk-covid-19-vaccines-delivery-plan-final.pdf">by the autumn of 2021</a>. It’s likely that any vaccine booster programme will only begin afterwards. Indeed, the logistics of planning, procuring the boosters, distributing them and rolling them out is fairly complex. This may delay rollout to early 2022.</p>
<h2>Will the booster be an updated formula?</h2>
<p>So far, the vaccines in use in the UK are <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/971017/SP_PH__VE_report_20210317_CC_JLB.pdf">showing good efficacy</a> against circulating variants of the virus. On that basis, booster vaccines are likely to be the same as ones used previously. </p>
<p>However, a major concern is that a new variant emerges that can evade the immunity provided by existing vaccines – what’s known as “vaccine escape”. </p>
<p>Should an escape variant emerge, one strategy may be to boost people with the existing vaccine that has the best efficacy against it. For example, the B1351 variant identified in South Africa appears to have some escape potential, as the Oxford/AstraZeneca vaccine is <a href="https://www.cidrap.umn.edu/news-perspective/2021/03/astrazeneca-vaccine-doesnt-prevent-b1351-covid-early-trial">less effective</a> at preventing mild to moderate COVID-19 when facing it. However, <a href="https://www.nature.com/articles/d41586-021-01222-5">early research</a> – <a href="https://www.medrxiv.org/content/10.1101/2021.04.06.21254882v1">some of which</a> still needs to be reviewed by other scientists – suggests the Pfizer/BioNTech vaccine isn’t so severely affected.</p>
<p>If none of the existing vaccines are sufficiently effective, then updated vaccines may be needed. However, they will take time to alter and mass produce. In the meantime, we need to closely monitor and study both the emergence of new variants as well as the effectiveness of existing vaccines against them.</p>
<figure class="align-center ">
<img alt="Vials of the AstraZeneca, Pfizer and Moderna COVID-19 vaccines" src="https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/401243/original/file-20210518-17-1morxt3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Pfizer, Moderna and AstraZeneca have all started work on updated boosters to better handle the new variants.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/montreal-ca-16-march-2021-vials-1937221621">Marc Bruxelle/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Will I get a booster from a different manufacturer?</h2>
<p>Possibly. Combining COVID-19 vaccines that <a href="https://theconversation.com/how-the-leading-coronavirus-vaccines-work-146969">generate immunity in different ways</a> – such as Pfizer’s and AstraZeneca’s – could generate a more powerful and long-lasting immune response. It could also allow for greater flexibility in rolling out a third dose, which might speed things up.</p>
<p>However, while in theory mixing doses could give an extra boost of immunity, <a href="https://comcovstudy.org.uk/home">research</a> is still trying to work out if this actually happens. UK scientists looking at mixing the Pfizer and AstraZeneca vaccines have so far found that <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01115-6/fulltext">side-effects are more likely</a> when combining the two. On that basis, if an individual has reacted well to one vaccine, it may be sensible for the same vaccine to be used. </p>
<h2>Will I need another booster in the future?</h2>
<p>It will take more time to be sure, but again, possibly yes. This is still a new pandemic, and it’s <a href="https://science.sciencemag.org/content/372/6540/363">still not known conclusively</a> how long COVID-19 immunity lasts and how strong it will be. Based on what we know about the original Sars virus, <a href="https://www.jimmunol.org/content/186/12/7264.short">immune responses can last years</a> but may wane. What’s not known is whether these immune responses are sufficient to protect against severe illness or death.</p>
<p>It may therefore be prudent for people to be re-immunised against COVID-19 on an annual basis to maintain immunity, as <a href="https://www.nature.com/articles/d41586-021-00396-2">many scientists believe</a> the coronavirus will become endemic and circulate continually. If variants continue to emerge, then continually updated vaccines may become the norm, like for seasonal flu.</p>
<p>There’s also emerging evidence that COVID-19 vaccines don’t just protect against disease, but also <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7020e2.htm?s_cid=mm7020e2_e">reduce the probability</a> of people spreading the virus by <a href="https://www.nature.com/articles/s41591-021-01316-7">reducing the amount of virus</a> infected people carry. Vaccinations could therefore be used on an ad hoc basis to quell outbreaks and emerging epidemics.</p>
<p>There remain many unanswered questions, and how the global pandemic will unfold in the next year is also uncertain. Vaccine policy decisions will need to be flexible and informed by emerging evidence of vaccine effectiveness and infection trends.</p><img src="https://counter.theconversation.com/content/160888/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Lee has previously received research funding from the National Institute for Health Research. He is a member of the UK Faculty of Public Health and the Royal Society for Public Health.</span></em></p>A public health expert outlines what Britons can expect from their upcoming booster programme.Andrew Lee, Reader in Global Public Health, University of SheffieldLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1602282021-05-14T12:37:43Z2021-05-14T12:37:43ZHerd immunity appears unlikely for COVID-19, but CDC says vaccinated people can ditch masks in most settings<figure><img src="https://images.theconversation.com/files/400555/original/file-20210513-24-1oi0y2i.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4266%2C2623&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A woman walks by a sign in New York City amid the coronavirus pandemic on March 30, 2021.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/person-walks-by-a-sign-that-reads-the-vaccine-is-our-best-news-photo/1310072796?adppopup=true">Noam Galai/Getty Images</a></span></figcaption></figure><p><em>When COVID-19 first began spreading, public health and medical experts began talking about the need for the U.S. to reach herd immunity to stop the coronavirus from spreading. Experts have estimated that between 60% and 90% of people in the U.S. would need to be vaccinated for that to happen. Only about <a href="https://www.nytimes.com/interactive/2020/us/covid-19-vaccine-doses.html">35% of the population has been fully vaccinated</a>, and yet the CDC said on May 14, 2021 that <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated.html">fully vaccinated people can lose their masks in most indoor and outdoor settings</a>.</em> </p>
<p><em>An important question now arises: What happens if we don’t reach herd immunity? Dr. William Petri is a professor of infectious diseases at the University of Virginia who helps lead the global program to achieve herd immunity for polio as the chair of the World Health Organization’s Polio Research Committee. He answers questions here about herd immunity and COVID-19.</em></p>
<h2>What is herd immunity?</h2>
<p>Herd immunity occurs when there are enough immune people in a population that new infections stop. It means that enough people have achieved immunity to disrupt person-to-person transmission in the community, thereby protecting nonimmune people. </p>
<p>Immunity can result from either vaccination or prior infection. Herd immunity may exist globally, as it does with smallpox, or in a country or region. For example, the U.S. <a href="https://doi.org/%2010.1098/rstb.2013.0433">and many other countries</a> have achieved herd immunity for polio and measles, even though global herd immunity does not yet exist.</p>
<h2>Has herd immunity been achieved globally for other infections?</h2>
<p>This has happened only once on a global scale, with <a href="https://www.cdc.gov/smallpox/history/history.html">the eradication of smallpox in 1980</a>. This was after a decadelong worldwide intensive vaccination campaign. </p>
<p>We also are also approaching global herd immunity for polio. When the <a href="https://polioeradication.org">Global Polio Eradication Initiative</a> was formed in 1988 there were 125 countries with endemic polio and over 300,000 children paralyzed annually. Today, after 33 years of immunization campaigns, Afghanistan and Pakistan are the only countries with wild polio virus, with only <a href="https://science.sciencemag.org/content/368/6489/362.abstract">two cases of paralysis due to wild poliovirus this year</a>. So herd immunity can be achieved worldwide, but only through extraordinary efforts with global collaboration.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/RgYvwj_Q2M4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Dr. Anthony Fauci explains herd immunity at a hearing before Congress.</span></figcaption>
</figure>
<h2>It seems as though the goal posts for herd immunity keep changing. Why?</h2>
<p>Experts estimate that between <a href="https://covid19-projections.com/path-to-herd-immunity/">60% and 90% of the U.S. population</a> would need to be immune for there to be herd immunity. This wide range is because there are many moving parts that determine what is needed to achieve herd immunity. </p>
<p>Factors influencing whether the target is 60% or 90% include how well vaccination and prior infection prevent not only illness due to COVID-19, but also infection and transmission to others. Additional considerations include the <a href="https://doi.org/10.1038/d41586-021-00728-2">heightened transmissibility of new variants of SARS-CoV-2</a> and the <a href="https://doi.org/10.1038/d41586-021-00728-2">use of measures to interrupt transmission</a>, including face masks and social distancing. Other important factors include the duration of immunity after vaccination or infection, and environmental factors such as seasonality, population sizes and density and heterogeneity within populations in immunity.</p>
<h2>What is the biggest barrier to herd immunity in the U.S.?</h2>
<p>Two factors could lead to failure to achieve high enough levels of immunity: not every adult receiving the vaccine because of “vaccine hesitancy” and the likely need to vaccinate adolescents and children. The FDA cleared the <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-pfizer-biontech-covid-19-vaccine-emergency-use">emergency use of the Pfizer-BioNTech COVID-19 vaccine</a> for adolescents 12 to 15 years of age on May 10, 2021, so that could help. But an added barrier is the constant pressure of reintroduction of infection from other countries where vaccination is not as readily available as in the U.S. </p>
<p>Achieving herd immunity to the extent of totally blocking new infections is therefore, while a laudable goal, not easily achievable. I think that for COVID-19 at this time, it will be possible only with the concerted global effort over years, similar to what led to smallpox eradication.</p>
<h2>Why are there ‘vaccine hesitant’ individuals?</h2>
<p>People may be vaccine hesitant for several reasons, including lack of confidence in the vaccine, the inconvenience of receiving the vaccine, or complacency – that is, <a href="https://doi.org/10.1016/j.vaccine.2015.04.036">thinking that if they get COVID-19 it will not be severe</a>. </p>
<p>Lack of confidence includes concerns for vaccine safety or skepticism about the health care providers and public health officials administering them. Complacency reflects a personal decision that vaccination is not a priority for that individual because she or he perceives that the infection is not serious or because of competing priorities for time. Convenience issues include the availability and complexity, such as having to get two doses. </p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p>
<h2>Since herd immunity will not be reached, what will our lives look like?</h2>
<p>At least into 2022 and likely for much longer, I do not expect there will be herd immunity for COVID-19. What there will be, probably by the end of this summer in the U.S., is a new normalcy. There will be far fewer cases and deaths due to COVID-19, and there will be a removal of social distancing and year-round masking, as evidenced by the CDC’s new guidelines issued May 13, 2021, that <a href="https://www.nytimes.com/2021/05/13/health/cdc-masks-guidance.html">vaccinated people do not have to wear masks in most places</a>. </p>
<p>But there will be a seasonality to coronavirus infections. That means there will be less in the summer and more in the winter. We’ll also see outbreaks in regions and population subgroups that lack adequate immunity, short-lived lockdowns of cities or regions, new and more transmissible variants and a <a href="https://www.cnbc.com/2021/05/11/covid-booster-shots-cdc-director-says-us-planning-just-in-case.html">likely requirement for vaccine booster shots</a>. We cannot let down on the research and development of treatments and new vaccines, as studies show that <a href="https://doi.org/10.1038/d41586-021-00728-2">COVID-19 is here to stay</a>.</p><img src="https://counter.theconversation.com/content/160228/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Petri receives research funding from the NIH, the Gates Foundation and Regeneron Inc.</span></em></p>Vaccination rates for COVID-19 have been lower than desired for herd immunity, or when enough people become immune for new infections to stop. What will life look like without it?William Petri, Professor of Medicine, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1566152021-03-19T11:29:36Z2021-03-19T11:29:36ZHow effective is the first shot of the Pfizer or Moderna vaccine?<figure><img src="https://images.theconversation.com/files/411570/original/file-20210715-52849-4vv9ib.jpg?ixlib=rb-1.1.0&rect=152%2C73%2C3234%2C2360&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Make that second appointment and get your final dose for full protection.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/detail-photo-of-the-back-of-a-covid-19-vaccination-record-news-photo/1316475438">MediaNews Group/Reading Eagle via Getty Images</a></span></figcaption></figure><p>Maybe you’ve postponed your second COVID-19 vaccine appointment, whether because of scheduling hassles or general reluctance. But how safe are you after just a single dose?</p>
<p><a href="https://scholar.google.com/citations?user=6yMIM1MAAAAJ&hl=en">As an immunologist</a>, I hear this question frequently – and the answer has changed as new genetic strains of the coronavirus become more common. <a href="https://covid.cdc.gov/covid-data-tracker/?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fcoronavirus%2F2019-ncov%2Fcases-updates%2Fvariant-proportions.html#variant-proportions">By the beginning of July 2021</a>, the <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-info.html">delta variant</a> had become the most dominant strain of SARS-CoV-2 circulating in the U.S.</p>
<p>The Moderna and Pfizer mRNA vaccines weren’t designed specifically to ward off the delta variant. While overall they still <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness.html">provide excellent protection</a> after the full two doses, new research suggests <a href="https://doi.org/10.1038/s41586-021-03777-9">a single dose provides less immunity</a> against the coronavirus strains that are out there now than it did against the original strain.</p>
<p>Bottom line: Two shots are way better than one.</p>
<figure class="align-center ">
<img alt="Nurses prepare to give medical workers vaccines." src="https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390402/original/file-20210318-21-1xg2fuo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Medical workers receive vaccination against COVID-19 on Dec. 20, 2020, in Tel Aviv.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/medical-workers-vaccinate-medical-stuff-members-against-news-photo/1230224367?adppopup=true">Amir Levy/Getty Images</a></span>
</figcaption>
</figure>
<h2>How well had the vaccines been working?</h2>
<p>Soon after the Pfizer COVID-19 vaccine was authorized in December 2020, researchers in Israel found that a <a href="https://doi.org/10.1016/S0140-6736(21)00448-7">single dose was highly effective</a> in one medical center’s thousands of vaccinated health care workers. A single dose reduced the rate of infection by up to 85% after four weeks post-shot compared to those who were not vaccinated.</p>
<p>This real-world finding was consistent with an analysis <a href="https://doi.org/10.1056/NEJMoa2034577">of Pfizer’s clinical trial data</a> reported in 2020 in the New England Journal of Medicine. In that study, the 52% protection from the first dose included infections that occurred in the first 12 days after vaccination, when one would not expect the vaccine to have had time to generate protective antibodies.</p>
<p>Another real-world study of adults ages 70 and older conducted by Public Health England in early 2021 determined that <a href="https://doi.org/10.1136/bmj.n1088">a single dose of the Pfizer vaccine was 61% effective</a> at preventing symptomatic disease 28 days after vaccination. Two doses increased effectiveness to 85%-90%.</p>
<h2>So, what’s changed?</h2>
<p>Essentially, it comes down to new variants. Scientists are particularly concerned about the delta variant because it <a href="https://www.nytimes.com/2021/07/15/briefing/delta-variant-spread-contagious.html">appears to be especially contagious</a>.</p>
<p>All of the vaccines for COVID-19 <a href="https://doi.org/10.1038/s41586-021-03738-2">generate antibodies against the spike glycoprotein</a> on the surface of the coronavirus. If you encounter the coronavirus after you’ve been vaccinated, these antibodies protect you by binding to the spike on its surface, preventing the virus from entering your cells to cause an infection.</p>
<p>The problem is that the delta variant can evade some – but not all – of the antibodies generated by the current vaccines.</p>
<h2>How well do vaccines protect against delta so far?</h2>
<p>It looks like the delta variant is relatively resistant to the anti-spike antibodies vaccination generates. This change is what makes it all the more important to get the second dose of an mRNA vaccine.</p>
<p>The first shot <a href="https://doi.org/10.1038/s41577-020-00479-7">introduces your body</a> to the virus’s spike protein so your immune system can start to produce targeted antibodies and immune cells. <a href="https://theconversation.com/why-it-takes-2-shots-to-make-mrna-vaccines-do-their-antibody-creating-best-and-what-the-data-shows-on-delaying-the-booster-dose-153956">The second shot</a> gives your body another chance to practice mounting that immune response against COVID-19. The second dose triggers the creation of more anti-spike antibodies, and these are more effective at protecting you because they bind more tightly to the viral spike if they encounter it.</p>
<p>In a study published in the journal Nature in July, researchers tested serum from the blood of 16 recent Pfizer vaccine recipients in France. After the first dose of the mRNA vaccine, serum from <a href="https://doi.org/10.1038/s41586-021-03777-9">only two of the 16 vaccinated people neutralized the delta variant</a> of the virus. The good news, though, is that after the second vaccine dose, serum from 15 out of 16 people neutralized the delta variant.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="masked people walk past a public Christmas tree" src="https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/411572/original/file-20210715-25-1hqj2pl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The delta variant started gaining a foothold in the U.K. at the end of 2020.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/pedestrians-wearing-a-protective-face-covering-to-combat-news-photo/1229735590">Tolga Akmen/AFP via Getty Images</a></span>
</figcaption>
</figure>
<p>Out of the lab and in the real world, Public Health England has collected data on all symptomatic cases of COVID-19 in the country in which the coronavirus was genetically sequenced. Of the 1,054 cases of delta infection through the middle of May 2021, a preliminary analysis that has not yet been peer-reviewed found that <a href="https://doi.org/10.1101/2021.05.22.21257658">one dose of the Pfizer vaccine was 33% effective</a> at preventing symptomatic infection. Protection rose to 88% after two doses. Those protection levels for delta are lower than what they found for the older alpha variant: 51% effectiveness after dose one and 93% after dose two.</p>
<p>A smaller preliminary study from Canada that also has not yet been peer-reviewed identified a <a href="https://doi.org/10.1101/2021.06.28.21259420">similar level of protection</a>. In 165 people with delta infection, researchers found 56% protection from symptomatic infection with one dose of Pfizer and 87% with two. Importantly, researchers calculated that protection from hospitalization or death from delta after even a single dose was 78% for Pfizer and 96% for Moderna.</p>
<h2>Am I protected?</h2>
<p>You are well protected if you have completed your vaccination: two doses of the Pfizer or Moderna or the single-dose Johnson & Johnson vaccine. If you have had only one of the two required doses of the mRNA vaccines, then you should finish vaccination by getting the second shot. That will raise your COVID-19 protection from what <a href="https://doi.org/10.1101/2021.05.22.21257658">might be as low as 33%</a> better than an unvaccinated person <a href="https://www.cdc.gov/vaccines/covid-19/effectiveness-research/protocols.html">up to 90%</a>.</p>
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<p>The picture is more complicated if you are immunocompromised. Studies have found that <a href="https://doi.org/10.1126/sciimmunol.abj1031">some immunocompromised patients</a> <a href="https://doi.org/10.7326/M21-1451">don’t produce antibodies</a> after vaccination. In these cases, some studies suggest that <a href="https://doi.org/10.7326/L21-0282">booster shots may offer hope</a>, with a third dose of an mRNA vaccine triggering a protective antibody response.</p>
<p>For mRNA vaccines against COVID-19, the <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html">CDC recommendation remains the same</a>: For Pfizer, get two doses 21 days apart, and for Moderna, get two doses 28 days apart. Sticking to the schedule and getting both doses means you will have very high levels of protection once your body has time to build immunity.</p>
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<p><em>Editor’s note: Since this article was initially published on March 19, 2021, the coronavirus has continued to mutate. This updated version reflects research as of July 2021 suggesting that a single dose of the Moderna or Pfizer COVID-19 vaccine is not enough to reliably ward off infection. The recommendation remains to receive the full course of two shots.</em></p><img src="https://counter.theconversation.com/content/156615/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Petri receives funding from National Institutes of Health, the Gates Foundation and Regeneron.</span></em></p>An immunologist explains that you get some protection from the first dose of the mRNA vaccines but you need two to build up strong immunity, particularly to newer coronavirus variants.William Petri, Professor of Medicine, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.