tag:theconversation.com,2011:/nz/topics/b-1-351-98944/articlesB.1.351 – The Conversation2021-04-16T00:44:52Ztag:theconversation.com,2011:article/1590322021-04-16T00:44:52Z2021-04-16T00:44:52ZCOVID-19 variants FAQ: How did the U.K., South Africa and Brazil variants emerge? Are they more contagious? How does a virus mutate? Could there be a super-variant that evades vaccines?<figure><img src="https://images.theconversation.com/files/395131/original/file-20210414-18-4tk56l.jpg?ixlib=rb-1.1.0&rect=12%2C67%2C4077%2C3145&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Colorized scanning electron micrograph of a cell (orange) infected with UK B.1.1.7 variant SARS-CoV-2 virus particles (green), isolated from a patient sample. Image captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland.
</span> <span class="attribution"><span class="source">(NIAID)</span></span></figcaption></figure><p>More and more countries around the world are struggling with a <a href="https://covid19.who.int/">new wave of infections</a>, with an alarming increase in COVID-19 cases. Mostly these new surges are attributed to <a href="https://www.gisaid.org/hcov19-variants/">variants of SARS-CoV-2</a>. </p>
<p>In lay terms, a variant refers to a virus genetically distinct from its <a href="https://www.virology.ws/2021/02/25/understanding-virus-isolates-variants-strains-and-more/">original strain</a>. The emergence of variants in the microbial world is nothing new, just think of “superbugs” such as <a href="https://www.mayoclinic.org/diseases-conditions/mrsa/symptoms-causes/syc-20375336">MRSA</a> (methicillin-resistant Staphylococcus aureus), which is <a href="https://doi.org/10.1074/jbc.M706296200">resistant to almost all the existing antibiotics</a>.</p>
<h2>How did the U.K., South Africa and Brazil variants emerge?</h2>
<p>Genetic transformation of a virus occurs by mutation. Mutations emerge naturally in the microbial world. They are mistakes in the genetic code caused by copying processes in the cell. These mistakes are exploited by the virus to survive and establish itself, especially under adverse conditions. </p>
<p>Curiously, viruses mutate at a much higher rate than other micro-organisms. Often mistakes in the genetic code come and go without leaving any traces, but in a few instances, they are selected when they offer the microbe a growth (or infection) advantage. </p>
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Read more:
<a href="https://theconversation.com/drug-resistant-superbugs-a-global-threat-intensified-by-the-fight-against-coronavirus-135790">Drug-resistant superbugs: A global threat intensified by the fight against coronavirus</a>
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<p>In the case of SARS-CoV-2, several mutations have been selected, meaning they are propagated to the next generation of viruses. They are selected for efficient access to host cells — fewer viruses are needed to infect the host — and effective evasion of the neutralizing antibodies of the immune system, meaning they are able to dodge immune response so they can circulate longer in the host, providing more opportunity to infect other cells. </p>
<p>However, human intervention — such as the use of certain treatments like <a href="https://doi.org/10.1038/s41586-021-03291-y">convalescent plasma</a> or <a href="http://doi.org/10.1126/science.abd0831">monoclonal treatment</a> — can drive virus evolution in much the same way that <a href="https://doi.org/10.1002/0471238961.0114200913150201.a01">antibiotic use</a> drives the evolution of bacterial superbugs.</p>
<h2>How seriously should we take SARS-CoV-2 variants?</h2>
<figure class="align-right ">
<img alt="Electron micrograph of B.1.1.7 variant of SARS-CoV showing the protein spikes in blue" src="https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395374/original/file-20210415-21-hp177l.jpg?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">
<figcaption>
<span class="caption">The SARS-CoV-2 virus’s spike proteins give the coronavirus its crown-like shape. In this transmission electron micrograph of the U.K. B.1.1.7 variant, the spike proteins are seen as prominent projections (blue) on the outside of the virus particle.</span>
<span class="attribution"><span class="source">(NIAID)</span></span>
</figcaption>
</figure>
<p>The <a href="https://www.who.int/csr/don/31-december-2020-sars-cov2-variants/en/">World Health Organization (WHO) categorizes virus variants</a> into two different groups: variant of concern (VOC) and variant of interest (VOI). VOCs represent those variants that are linked to the rise of new infection waves in many countries, including the recent surges in Canada and United States. </p>
<p>Here in Canada, the B.1.1.7 variant, which <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/scientific-brief-emerging-variants.html">emerged in the United Kingdom</a> in September 2020, is <a href="https://www.ctvnews.ca/health/coronavirus/canada-sets-new-single-day-covid-19-record-with-9-244-cases-1.5382102">becoming the dominant variant</a>. </p>
<p>The other VOCs — such as B.1.351, first identified in South Africa, and P.1, first identified in Brazil — are being identified more often and <a href="https://www.cbc.ca/news/canada/edmonton/alberta-covid-coronavirus-p1-variant-1.5978751">have been responsible</a> for <a href="https://www.theguardian.com/world/2021/apr/11/canada-ski-resort-p1-covid-variant-whistler">several outbreaks</a> in <a href="https://www.cbc.ca/news/health/coronavirus-variants-canada-covid-19-vaccine-third-wave-1.5978394">Canada</a>.</p>
<p>There is evidence, some of which has not yet been peer reviewed, that VOCs are associated with higher virulence than the coronavirus that originated in Wuhan, China: <a href="https://doi.org/10.1101/2020.12.24.20248822">higher transmissibility</a>, possible <a href="https://doi.org/10.1016/S1473-3099(21)00170-5">higher disease severity</a> and, in the case of B.1.351, an increased ability to evade <a href="https://doi.org/10.1101/2021.03.01.433466">neutralizing antibodies</a>.</p>
<p>These attributes of VOCs have translated into higher hospitalizations of <a href="https://globalnews.ca/news/7738013/coronavirus-vaccinating-young-people/">younger people</a> and an <a href="https://doi.org/10.1136/bmj.n579">increase in deaths</a> across <a href="https://health-infobase.canada.ca/covid-19/epidemiological-summary-covid-19-cases.html?stat=rate&measure=total_last14&map=pt#a2">all age groups in Canada</a>.</p>
<p><a href="https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/variant-surveillance/variant-info.html">VOIs</a> are on the radars of public health agencies for their impact on virus transmission, the severity of disease and vaccine effectiveness.</p>
<h2>How does mutation change how a virus works?</h2>
<p>The genetic code of a virus provides instructions to make its proteins: strings of amino acids in defined sequences. Mutation can lead to amino acid substitution or deletion in the protein. The attention of the scientific community is focused on the amino acid substitutions that affect the SARS-CoV-2 spike protein, the protein that gives the virus its crown-like shape. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of how spike protein enters host cell" src="https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=172&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=172&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=172&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=217&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=217&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395347/original/file-20210415-21-6kqaep.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=217&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: Lock-and-key interaction of the SARS-CoV-2 spike protein with human ACE-2. Right: How a neutralizing antibody inhibits the ‘unlocking’ activity of spike protein.</span>
<span class="attribution"><span class="source">(UNC School of Medicine/Vivian Saradakis)</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The spike protein is the key that provides access to human cells via the human ACE-2 protein (the lock), and as such is the target of the currently approved COVID-19 vaccines. Research that has yet to be peer reviewed shows two ways in which changes to the amino acid sequence of the spike protein may affect its interaction with human cells: </p>
<ul>
<li>They can <a href="https://doi.org/10.1101/2021.02.14.431117">enhance the spike protein’s interaction</a> with ACE-2, providing efficient access to host cells.</li>
<li>They can decrease the spike protein’s <a href="https://doi.org/10.1101/2021.01.26.21250543">interaction with neutralizing antibodies</a>, helping it evade an immune system response long enough to infect other cells.</li>
</ul>
<p>Proteins can be thought of as microscopic Lego structures, with amino acids behaving as Lego pieces and held together by a single thread. However, protein structures are much more flexible than Lego structures (think of Lego pieces made of Jell-O), with the amino acids able to form transient bonds with other amino acids close to them as needed for structural stability and recognizing other structures. </p>
<p>The spike protein’s structural flexibility allows it to sample the space inside the lock (ACE-2) to enable recognition of the key, but also to find the optimum key-shape for that lock. It is the latter function that is optimized through mutation: the best key-shape will open the lock faster and more easily. </p>
<h2>Could mutation lead to a super-variant that can evade all vaccines?</h2>
<p>Many VOCs and VOIs have been identified around the world, and more variants get reported daily (about one million variants have been <a href="https://outbreak.info/situation-reports">recorded to date</a>). Should we be afraid of the emergence of a super-variant, which is highly virulent and can overpower all current vaccines and any others in the future?</p>
<p>The three current VOCs that have taken hold in many countries carry several amino acid substitutions in their spike proteins. Because of the spike protein’s crucial role in entering cells, all of the COVID-19 vaccines currently available work by targeting the spike protein.</p>
<p>Peculiarly, a few of the amino acid substitutions in the spike protein are common to the three current VOCs and are considered to drive their dominance over other variants. Research that has yet to be peer reviewed shows the substitutions <a href="https://doi.org/10.1101/2021.02.14.431117">N501Y</a> (asparagine to tyrosine) and <a href="https://doi.org/10.1101/2021.03.10.434733">D614G</a> (aspartate to glycine) are common to all three, while E484K (glutamate to lysine) is common to B.1.351 and P.1. </p>
<p>The E484K substitution is believed to be responsible for <a href="https://doi.org/10.1101/2021.03.01.433466">antibody evasion</a>, and N501Y and D614G are thought to drive the higher <a href="https://virological.org/t/tracking-sars-cov-2-voc-202012-01-lineage-b-1-1-7-dissemination-in-portugal-insights-from-nationwide-rt-pcr-spike-gene-drop-out-data/600">transmissibility</a> of these variants. (The <a href="https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/variant-surveillance/variant-info.html">CDC website</a> offers more information on the attributes of the variants.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic depicting different amino acid substitutions in a spike protein" src="https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395350/original/file-20210415-16-1cp2n0m.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Top bar: SARS-CoV-2 gene organization. The gene that encodes the spike protein is denoted ‘S.’ Breakdown shows the amino acid substitutions identified in the spike proteins of different variants (the number indicates the position of the amino acid substituted, Δ indicates the amino acids that are deleted). The receptor binding site (RBS) that interacts with ACE-2 spans amino acids 331 to 527. (Data from https://outbreak.info/situation-reports).</span>
<span class="attribution"><span class="source">(Dasantila Golemi-Kotra)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It is curious that the common amino acid substitutions identified among VOCs emerged independently and in different parts of the globe. There are, in fact, 20 different amino acids provided by the host cell, all of which have an equal opportunity to substitute an amino acid in the protein through mutation. Yet, remarkably, these three VOCs evolved to acquire some of the same amino acid substitutions! </p>
<p>This phenomenon is referred to in biology as convergence evolution: when the same feature evolves independently. This means that the selected amino acids offer a unique property that makes the virus “fitter.”</p>
<p>The spike protein has an important function: it has to unlock <a href="https://doi.org/10.1038/nature02145">access to the host cell</a>, but it is also the target of <a href="https://doi.org/10.1016/j.scr.2020.102125">neutralizing antibodies</a>, which the virus has to prevent from latching onto the protein in order to evade the immune system. Both these functions rely on the same part of the protein: the receptor binding domain (RBD).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three images of pink spike proteins with antibodies in yellow" src="https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=303&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=303&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=303&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=381&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=381&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395351/original/file-20210415-15-17h5itu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=381&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Structure of spike protein with three different antibodies (C002, S2M11, EY6A) isolated from patients. All three bind to the receptor-binding domain (RBD) of the spike, but in different regions.</span>
<span class="attribution"><a class="source" href="http://pdb101.rcsb.org/motm/256">(David S. Goodsell/RCSB Protein Data Bank)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Enhancement of one of these two functions can diminish the other function. That means a compromise has to be reached. The fact that the same substitutions arose independently in different variants is an indication that the spike proteins in these variants have been optimized, and may not gain any further advantages. </p>
<p>Based on this, emergence of a super-variant seems unlikely, because these two functions — unlocking the host cell and evading the immune system — will always be in competition with each other, so neither will be able to achieve perfect efficiency.</p>
<p>However, never underestimate the force of evolution when there is a fertile playing field. We must adhere to public health measures, such as social distancing and masks, to mitigate the spread of the virus and limit the number of hosts that the virus can infect, for <a href="https://theconversation.com/covid-19-vaccine-faqs-efficacy-immunity-to-illness-vs-infection-yes-theyre-different-new-variants-and-the-likelihood-of-eradication-154569">as long as most of the population remains unvaccinated</a>.</p><img src="https://counter.theconversation.com/content/159032/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dasantila Golemi-Kotra 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>Variants of the original SARS-CoV-2 are now in wide circulation. That means the third wave of COVID-19 has come with new questions about the variants, their effects and what might come next.Dasantila Golemi-Kotra, Professor, Biology, York University, CanadaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1583022021-04-11T11:47:56Z2021-04-11T11:47:56ZAstraZeneca COVID-19 vaccine FAQ: Why do the age recommendations keep changing? Does it cause VIPIT blood clots? Is it effective against variants?<figure><img src="https://images.theconversation.com/files/393921/original/file-20210408-17-njzf41.JPG?ixlib=rb-1.1.0&rect=0%2C0%2C3467%2C2592&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The AstraZeneca vaccine was 70 per cent effective against symptomatic COVID-19 infection in a large multinational study, and recently reported 76 per cent overall efficacy against symptomatic COVID-19 in another large study done primarily in the United States. </span> <span class="attribution"><span class="source"> THE CANADIAN PRESS/John Woods </span></span></figcaption></figure><p>Many people have questions about the changing guidelines for the use of AstraZeneca’s COVID-19 vaccine. Here are some answers from infectious disease specialist Dr. Alexander Wong. </p>
<h2>How is the AstraZeneca vaccine different from the other COVID-19 vaccines?</h2>
<p>ChADOx1 nCoV-19/AZD1222 (AstraZeneca’s COVID-19 vaccine, also called the Oxford-AstraZeneca vaccine and COVISHIELD) uses a <a href="https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/viralvector.html">modified adenovirus “vector</a>” to deliver the genetic code for the SARS-CoV-2 <a href="https://theconversation.com/new-coronavirus-variant-what-is-the-spike-protein-and-why-are-mutations-on-it-important-152463">spike protein</a> to the cell nucleus. This vector has been modified so that it can enter human cells, but once inside, it cannot replicate. That means it can’t cause danger to the vaccine recipient.</p>
<p>Once inside the cell, the DNA for the spike protein is delivered to the cell nucleus. There, the code is translated into messenger RNA (mRNA) that the cell can then use to manufacture its own spike proteins. </p>
<p>These spike proteins then help to stimulate the body’s immune system to develop antibodies. It is these antibodies that help protect us from infection and severe illness when we are exposed to the SARS-CoV-2 virus.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="New Brunswick Premier Blaine Higgs getting an injection" src="https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393923/original/file-20210408-13-v2u4x6.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">New Brunswick Premier Blaine Higgs receives the Oxford-AstraZeneca COVID-19 vaccine in Fredericton on March 31. Administering the vaccine is Brenda Tree of Pharmacy for Life.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Stephen MacGillivray</span></span>
</figcaption>
</figure>
<p>AstraZeneca vaccine is different than the mRNA vaccines (such as Pfizer-BioNTech and Moderna). The adenovirus “vector” and the DNA code that the vector transports are much more resilient and hardy compared to the lipid particles that hold the fragile mRNA code to be delivered into cells with the Pfizer-BioNTech and Moderna vaccines.</p>
<p>This leads to several practical advantages with AstraZeneca vaccine compared to mRNA vaccines — it does not have to stay frozen while stored and it can last for months at regular fridge temperatures. It is also less expensive to produce in large quantities.</p>
<p>The AstraZeneca vaccine was <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32661-1/fulltext">70 per cent effective against symptomatic COVID-19</a> infection in a large multinational study. Another large study done primarily in the United States <a href="https://www.astrazeneca.com/content/astraz/media-centre/press-releases/2021/azd1222-us-phase-iii-primary-analysis-confirms-safety-and-efficacy.html">recently reported 76 per cent overall efficacy against symptomatic COVID-19</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/covid-19-vaccines-how-pfizers-and-modernas-95-effective-mrna-shots-work-149957">COVID-19 vaccines: How Pfizer's and Moderna's 95% effective mRNA shots work</a>
</strong>
</em>
</p>
<hr>
<p>While these efficacy data are slightly less than the reported efficacy from mRNA vaccines, AstraZeneca vaccine is completely effective at preventing severe illness and hospitalizations, like mRNA vaccines. </p>
<p>The overall efficacy differences between AstraZeneca vaccine and mRNA vaccines are minor. For most persons in Canada, the best vaccine is typically the one that you’re offered first, especially amid the current third wave sweeping across the country.</p>
<h2>Why has its use been suspended in some areas? Is it linked to blood clots?</h2>
<p>In early March, reports from various countries in the European Union linked use of AstraZeneca vaccine to the potential for rare but potentially fatal blood clots, termed “<a href="https://covid19-sciencetable.ca/sciencebrief/vaccine-induced-prothrombotic-immune-thrombocytopenia-vipit-following-astrazeneca-covid-19-vaccination-interim-guidance-for-healthcare-professionals-in-emergency-department-and-inpatient-settings/">vaccine induced prothrombotic immune thrombocytopenia</a>,” or VIPIT. <a href="https://doi.org/10.1055/a-1469-7481">Data from Germany</a> suggest an incidence rate of roughly one per 90,000 shots. A recent update from the European Medicines Agency suggests <a href="https://www.nytimes.com/2021/04/07/world/europe/astrazeneca-uk-european-union.html?action=click&module=Top%20Stories&pgtype=Homepage">an incidence rate of one per 100,000 shots</a> across Europe thus far. </p>
<p>Researchers speculate that the vaccine may cause platelets to begin clotting, similar to a rare phenomenon caused by <a href="https://myhealth.alberta.ca/Health/aftercareinformation/pages/conditions.aspx?hwid=abr9773">heparin, a blood thinner</a>. Data is still emerging around the potential association between AstraZeneca vaccine and VIPIT, and the degree of risk remains unclear.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A health-care worker in a mask holding a vial of AstraZeneca's COVID-19 vaccine" src="https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=529&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=529&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393922/original/file-20210408-17-rbkaxr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=529&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A health-care worker holds up a vial of the AstraZeneca Covishield vaccine at a COVID-19 vaccination clinic in Montréal.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Paul Chiasson</span></span>
</figcaption>
</figure>
<p>On March 31, <a href="https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/rapid-response-recommended-use-astrazeneca-covid-19-vaccine-younger-adults.html">Canada suspended the use of AstraZeneca vaccine to all those under the age of 55</a>. <a href="https://www.bbc.com/news/world-europe-56580728">Germany did the same, but in all those under the age of 60</a>. <a href="https://www.ctvnews.ca/health/coronavirus/u-k-advises-limiting-astrazeneca-in-under-30s-amid-clot-worry-1.5377452">The United Kingdom suspended use in all those under the age of 30</a>.</p>
<p>The reasoning in Canada (and other countries) for the age-related pause on the use of AstraZeneca has to do with a calculation of risk versus benefit for a given individual. The overall risk of death in persons under the age of 55 who acquire COVID-19 infection is very low in Canada. </p>
<p>When comparing the risk of death from COVID-19 in younger persons versus the risk of VIPIT from AstraZeneca vaccine, regulators made the decision to be cautious with their guidance, especially because Canadians have access to <a href="https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines.html">other vaccines such as Moderna and BioNTech-Pfizer</a> and soon <a href="https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/janssen.html">Johnson & Johnson</a> vaccine as well. </p>
<p>As the evidence evolves, guidance for the use of AstraZeneca vaccine will likely change again.</p>
<h2>Why are there different recommendations for different age groups — and why do they keep changing?</h2>
<p>As described in the previous answer, there is an inherent balance between risk and benefit that expert groups needed to navigate when issuing guidance around AstraZeneca vaccine in the absence of definitive data. As we get older, our risk of dying of COVID-19 infection also increases. Thus, the balance between risk and benefit tips towards administration of the vaccine, which significantly reduces the likelihood of severe illness, hospitalization and death. </p>
<p>In younger people, this balance is more complicated, especially now with <a href="https://nccid.ca/covid-19-variants/">widespread circulation of variants of concern across Canada</a>. These variants are known to be more transmissible and more deadly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Boxes of vaccine inside a larger shipping box" src="https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393925/original/file-20210408-15-9sdy72.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">Boxes of AstraZeneca COVID-19 vaccine doses at a facility in Milton, Ont.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Carlos Osorio - POOL</span></span>
</figcaption>
</figure>
<p>Early in March, initial recommendations from the <a href="https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci.html">National Advisory Committee on Immunization</a> (NACI) in Canada suggested that AstraZeneca vaccine <a href="https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines/summary-updated-statement-16-march-2021.html">not be used in persons over the age of 65</a>. </p>
<p>This was because the initially reported clinical trial data from December included a very limited number of people over the age of 65, so the efficacy of the vaccine could not be determined in this age group. </p>
<p>Shortly thereafter, supportive real-world evidence generated from the United Kingdom was reviewed by NACI and deemed to be sufficient to illustrate the efficacy of AstraZeneca vaccine in persons over the age of 65, and recommendations changed accordingly.</p>
<p>The changing recommendations by NACI and other guideline groups are a reflection of changing evidence and science, not the inadequacy of the vaccine itself. This is precisely how <a href="https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection/prevention-risks/covid-19-vaccine-treatment/safety-after-authorization.html">post-marketing surveillance</a> is supposed to work with medicines and vaccines. </p>
<p>However, with such incredible scrutiny of this topic as a result of the global pandemic, trying to explain these concepts to the lay public has been challenging for regulators, public officials and health-care professionals alike.</p>
<h2>What should I do if I’ve already had one dose of the vaccine, but it’s no longer recommended for my age group?</h2>
<p>At present, this is unclear. Various studies are underway looking at combining different COVID-19 vaccines, <a href="https://www.bbc.com/news/health-55924433">particularly in the U.K.</a>, but there isn’t a good evidence base for this yet.</p>
<p>Public health guidance will be updated as evidence emerges, but if the association between AstraZeneca vaccine and VIPIT continues to hold firm, my best guess is that people in this situation will be offered a second dose of vaccine, but from a different manufacturer. Right now the current guidance remains to try not to administer different vaccines at different time points, if possible.</p>
<h2>Is it effective against the new variants?</h2>
<p>Data for the efficacy of AstraZeneca vaccine against the predominant circulating variants remains limited. <a href="https://doi.org/10.1016/S0140-6736(21)00628-0">Published data from clinical trials</a> suggests that the vaccine remains effective against the B.1.1.7 variant found predominantly in the U.K., even though the vaccine induced lower blood levels of antibodies against the B.1.1.7 variant compared to the non-mutated virus. </p>
<p><a href="http://doi.org/10.1056/NEJMoa2102214">Preliminary published data from South Africa</a> at a time when the B.1.351 variant was circulating widely suggested AstraZeneca vaccine had no reduction in the rate of mild to moderate COVID-19 infection in mostly young and healthy persons. However the trial included only small numbers overall. </p>
<p>The ability of the AstraZeneca vaccine to limit severe disease and hospitalization against the South African variant could also not be determined in this study due to very low numbers of young people otherwise becoming severely ill. More data is needed to better answer this question.</p><img src="https://counter.theconversation.com/content/158302/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Alexander Wong has previously received an honorarium for leading a scientific discussion for healthcare professionals on AstraZeneca COVID-19 vaccine.</span></em></p>With changing recommendations about AstraZeneca’s COVID-19 vaccine making headlines, many people have questions about its use.Alexander Wong, Associate Professor, Infectious Diseases, University of SaskatchewanLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1535302021-01-21T21:48:37Z2021-01-21T21:48:37ZWhy new COVID-19 variants are on the rise and spreading around the world<figure><img src="https://images.theconversation.com/files/380025/original/file-20210121-17-1r712y0.jpg?ixlib=rb-1.1.0&rect=137%2C101%2C3730%2C2544&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Medical technician Amira Doudou prepares samples at the University Hospital Institute for Infectious Diseases in Marseille, France, Jan. 13, 2021, to study the highly contagious COVID-19 variant.</span> <span class="attribution"><span class="source">(AP Photo/Daniel Cole)</span></span></figcaption></figure><p>A new variant of coronavirus has swept across the United Kingdom and been detected in the United States, Canada and elsewhere. <a href="https://www.who.int/news/item/12-01-2021-global-scientists-double-down-on-sars-cov-2-variants-research-at-who-hosted-forum">Scientists are concerned</a> that these new strains may spread more easily. </p>
<p>As an evolutionary biologist, I study how mutation and selection combine to shape changes in populations over time. Never before have we had so much real-time data about evolution as we do with SARS-CoV-2: over <a href="https://www.gisaid.org">380,000 genomes</a> were sequenced last year.</p>
<p>SARS-CoV-2 has been mutating as it spreads, generating slight differences in its genome. These mutations allow scientists to trace who is related to whom across the <a href="https://nextstrain.org/ncov/global">family tree</a> of the virus.</p>
<p>Evolutionary biologists, including myself, have cautioned against over-interpreting the threat posed by mutations. Most mutations will not help the virus, just like randomly kicking a working machine is unlikely to make it better. </p>
<p>But every once in a while a mutation or suite of mutations gives the virus an advantage. The data are convincing that the mutations carried by the variant that first appeared in the U.K., known as B.1.1.7, make the virus more “fit.”</p>
<h2>Higher fitness or chance?</h2>
<p>When a new variant becomes common, scientists determine the reason behind its spread. A virus carrying a particular mutation can rise in frequency by chance if it is:</p>
<ul>
<li>carried by a superspreader;</li>
<li>moved to a new uninfected location;</li>
<li>introduced into a new segment of the population.</li>
</ul>
<p>The latter two examples are called “founder events”: a rapid rise in frequency can occur if a particular variant is introduced into a new group and starts a local epidemic. Chance events may explain the <a href="https://doi.org/10.1016/j.cub.2020.06.031">rise in frequency of several different SARS-CoV-2 variants</a>. </p>
<p>But B.1.1.7 is an exception. It shows a very strong signal of selection. For the past two months, B.1.1.7 has risen in frequency faster than non-B.1.1.7 in virtually every week and health region in England. <a href="https://www.gov.uk/government/publications/investigation-of-novel-sars-cov-2-variant-variant-of-concern-20201201">This data, reported</a> on Dec. 21, 2020, helped convince U.K. <a href="https://www.cnn.com/videos/world/2021/01/04/boris-johnson-full-speech-coronavirus-variant-england-lockdown-vpx.cnn">Prime Minister Boris Johnson to place much of the country under lockdown</a> and led to widespread travel bans from the U.K. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1347691064430374912"}"></div></p>
<p>The rise of B.1.1.7 cannot be explained by a founder event in new regions, because COVID-19 was already circulating across the U.K. Founder events in a new segment of the population (e.g., following a conference) also aren’t plausible given the widespread restrictions against large gatherings at the time.</p>
<p>Our ability to track the evolution of SARS-CoV-2 is due to the massive effort by scientists to share and analyze data in real time. But the incredibly detailed knowledge we have about B.1.1.7 is also due to just plain dumb luck. One of its mutations altered a section of the genome used to test for COVID-19 in the U.K., allowing <a href="https://virological.org/t/transmission-of-sars-cov-2-lineage-b-1-1-7-in-england-insights-from-linking-epidemiological-and-genetic-data/576">the picture of evolutionary spread to be drawn from more than 275,000 cases</a>. </p>
<h2>Evolution in action</h2>
<p>Epidemiologists have concluded that B.1.1.7 is more transmissible, but there are no signs that it is more deadly. Some researchers estimate that B.1.1.7 increases the number of new cases caused by an infected individual (called the reproductive number or Rt) by between <a href="https://virological.org/t/transmission-of-sars-cov-2-lineage-b-1-1-7-in-england-insights-from-linking-epidemiological-and-genetic-data/576">40 and 80 per cent</a>; another preliminary study found that <a href="https://doi.org/10.1101/2020.12.24.20248822">Rt increased by 50-74 per cent</a>.</p>
<figure class="align-center ">
<img alt="A women pushing a cart through a nearly empty airport." src="https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380037/original/file-20210121-15-1xmrigt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A woman pushes a luggage cart through Heathrow Airport in London, on Jan. 18, 2021.</span>
<span class="attribution"><span class="source">(AP Photo/Matt Dunham)</span></span>
</figcaption>
</figure>
<p>A 40-80 per cent advantage means that B.1.1.7 isn’t just a little more fit, it’s a lot more fit. Even when selection is this strong, evolution isn’t instantaneous. Our mathematical modelling, as well as that by <a href="https://covid19-sciencetable.ca/wp-content/uploads/2021/01/Update-on-COVID-19-Projections_January-12-2021_Final_English-2.pdf">others in Canada</a> and the <a href="https://www.nytimes.com/live/2021/01/16/world/covid-19-coronavirus#a-fast-spreading-variant-could-become-the-dominant-source-of-infection-in-the-us-by-march-cdc-says">U.S.</a>, shows that it takes B.1.1.7 a couple of months to reach its meteoric rise, because only a small fraction of cases initially carries the new variant. </p>
<p>For many countries, like the U.S. and Canada, where the number of COVID-19 cases has been precariously rising, a variant that increases transmission by 40-80 per cent threatens to push us over the top. It could lead to exponential growth in cases and overwhelm already threadbare medical care. Evolutionary change takes a while, buying us maybe a few weeks to prepare. </p>
<h2>More variants</h2>
<p>One surprise for researchers was that B.1.1.7 bears a remarkable number of new mutations. B.1.1.7 has accumulated 30-35 changes over the past year. B.1.1.7 doesn’t mutate at a higher rate, but it appears to have undergone a bout of rapid change in the recent past. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379429/original/file-20210119-23-1p1uyv7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Each dot represents a SARS-CoV-2 genome, with branches connecting related viruses to their ancestors. The centre representss the virus introduced into humans. The viruses furthest from the centre carry more mutations. Highlighted in gold are the three new variants.</span>
<span class="attribution"><a class="source" href="https://www.nextstrain.org">(NextStrain)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The virus may have been <a href="https://www.gov.uk/government/publications/investigation-of-novel-sars-cov-2-variant-variant-of-concern-20201201">carried by an immunocompromised individual</a>. People with weaker immune systems fight the virus constantly, with prolonged infections, recurrent rounds of viral replication and only a partial immune response to which <a href="https://doi.org/10.1056/NEJMc2031364">the virus is constantly evolving</a>.</p>
<p>Preliminary research reports that have yet to be verified have described two other variants of concern: one originally from <a href="https://www.doi.org/10.1101/2020.12.21.20248640">South Africa (B.1.351)</a> and one from <a href="https://virological.org/t/genomic-characterisation-of-an-emergent-sars-cov-2-lineage-in-manaus-preliminary-findings/586">Brazil (P1)</a>. Both variants show a recent history of excess mutations and rapid increases in frequency within local populations. Scientists are currently gathering the data needed to confirm that selection for higher transmission, not chance, is responsible.</p>
<h2>What changed to allow spread?</h2>
<p>Selection plays two roles in the evolution of these variants. First consider the role within those individuals in which the large number of mutants arose. <a href="https://virological.org/t/preliminary-genomic-characterisation-of-an-emergent-sars-cov-2-lineage-in-the-uk-defined-by-a-novel-set-of-spike-mutations/563">B.1.1.7’s 23 mutations</a> and P1’s 21 mutations aren’t randomly arrayed across the genome but clustered in the gene encoding the <a href="https://theconversation.com/new-coronavirus-variant-what-is-the-spike-protein-and-why-are-mutations-on-it-important-152463">spike protein</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-coronavirus-variant-what-is-the-spike-protein-and-why-are-mutations-on-it-important-152463">New coronavirus variant: what is the spike protein and why are mutations on it important?</a>
</strong>
</em>
</p>
<hr>
<p>One change in the spike, called N501Y, arose independently in all three variants, as well as in immunocompromised patients studied in the <a href="https://doi.org/10.1056/NEJMc2031364">U.S.</a> and <a href="https://doi.org/10.1101/2020.12.05.20241927">U.K.</a> Other changes in the spike (e.g. E484K, del69-70) are seen in two of the three variants.</p>
<p>Beyond the spike, the three variants of concern share one additional mutation that deletes a small part of the drably named “non-structural protein 6” (NSP6). We don’t yet know what the deletion does, but <a href="https://doi.org/10.4161/auto.29309">in a related coronavirus NSP6 tricks a cellular defence system and may promote coronavirus infection</a>. NSP6 also hijacks this system to help <a href="https://doi.org/10.1080/15548627.2020.1817280">copy the viral genome</a>. Either way, the deletion might alter the ability of the virus to take hold and replicate within our cells.</p>
<h2>Easier transmission</h2>
<p>The parallel evolution of the same mutations in different countries and in different immunocompromised patients suggests that they convey a selective advantage to evade the immune systems of the individuals in which the mutations occurred. For N501Y, this has been backed up by experiments <a href="https://doi.org/10.1126/science.abc4730">in mice</a>. </p>
<p>But what accounts for the higher transmission rate from individual to individual? This is challenging to answer because the many mutations that arose at once are now bundled together in these variants, and it could be any one or a combination of them that leads to the transmission advantage.</p>
<p>That said, several of these variants have arisen before on their own and haven’t led to rapid spread. One study showed that <a href="https://doi.org/10.1101/2020.12.20.20248581">N501Y had only a weak transmission advantage on its own</a>, rising rapidly only when coupled with the suite of mutations observed in B.1.1.7. </p>
<p>While the evolutionary story of COVID is still being written, one important message is emerging now. The 40-80 per cent transmission advantage of B.1.1.7, and potentially the other variants B.1.351 and P1, <a href="https://www.nytimes.com/live/2021/01/16/world/covid-19-coronavirus#a-fast-spreading-variant-could-become-the-dominant-source-of-infection-in-the-us-by-march-cdc-says">will overwhelm many countries in the next few months</a>. </p>
<p>We’re in a race against viral evolution. We must roll out vaccines as quickly as possible, stem the flow of variants by restricting interactions and travel, and get in front of spread by ramping up surveillance and contact tracing.</p><img src="https://counter.theconversation.com/content/153530/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Otto volunteers on the BC COVID-19 Modelling Group, the Board of The Nature Trust of British Columbia, and on the Species at Risk Advisory Committee to Canada's Minister of the Environment. She receives research funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p>Multiple COVID-19 variants are circulating around the world and becoming more common. These mutations can alter the ability of the virus to take hold and replicate within our cells.Sarah Otto, Killam University Professor in Evolutionary Biology, University of British ColumbiaLicensed as Creative Commons – attribution, no derivatives.