tag:theconversation.com,2011:/ca-fr/topics/zika-vaccine-28998/articlesZika vaccine – La Conversation2016-11-07T02:11:53Ztag:theconversation.com,2011:article/682272016-11-07T02:11:53Z2016-11-07T02:11:53ZExplainer: what are antibodies and why are viruses like dengue worse the second time?<figure><img src="https://images.theconversation.com/files/144513/original/image-20161104-25322-2248hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">For viruses like dengue, being injected with the pathogen as in a vaccine can open the door to secondary infections. </span> <span class="attribution"><span class="source">from www.shutterstock.com.au</span></span></figcaption></figure><p>Our immune system is like a highly trained army. It fends off invading pathogens, usually very effectively. The problem is that sometimes it makes mistakes and attacks us. This can result in <a href="https://theconversation.com/what-are-allergies-and-why-are-we-getting-more-of-them-40318">allergies</a>, <a href="https://theconversation.com/why-its-never-lupus-television-illness-and-the-making-of-a-meme-1198">autoimmune diseases</a> or just <a href="https://theconversation.com/explainer-how-viruses-can-fool-the-immune-system-43707">misfires in the immune system’s attack</a> of invading cells. </p>
<p>But there’s another way the immune system can fail us – by throwing down the welcome mat for viruses on their second invasion.</p>
<h2>What are antibodies?</h2>
<p>Our <a href="https://theconversation.com/explainer-what-is-the-immune-system-19240">immune systems are complex</a> but two components are critical: antibodies and macrophages. Antibodies are produced by the “memory cells” of the immune system so if you are ever challenged by the same infection again, you will be able to recognise it, respond much faster and kill the invaders. </p>
<p>Antibodies are made to attach to certain proteins on the surface of an invading organism, called antigens. By sticking to these antigens, antibodies block the invader’s ability to replicate, and enter cells, thereby rendering the invader useless. </p>
<p>Then the janitor cells of the immune system (macrophages, literally “big eaters”), search around for these “useless invaders” attached to antibodies, engulf them and chop them up for re-use or excretion. </p>
<p>However, some viruses actually get inside macrophages, using the antibodies as a Trojan horse. They pretend to be useless, getting engulfed by the macrophage and then converting the macrophage into a virus-producing machine. This is antibody-dependent enhancement.</p>
<h2>Antibody-dependent enhancement and mosquito-borne viruses</h2>
<p>There are hundreds of thousands of dengue cases across the world each year, making dengue viruses one of the most important mosquito-borne pathogens. There are four types of dengue and while infection with one virus will make you seriously ill, the symptoms can become potentially fatal when infected subsequently with a different strain. </p>
<p>This is because the antibodies made against the first virus type help the second virus to enter cells, resulting in dengue haemorrhagic fever. This is the severe and potentially deadly form of the disease characterised by haemorrhaging (bleeding from the nose or gums or extensive bruising under the skin), severe abdominal pain, vomiting, and fever.</p>
<p>Antibody-dependent enhancement was <a href="http://jem.rupress.org/content/jem/146/1/201.full.pdf">first recognised to occur</a> in humans with dengue in 1977; researchers noticed the disease was more severe in children who received maternal antibodies for dengue or adults who had previously been infected with a different type of dengue (serotype). </p>
<p>Researchers then tested this hypothesis experimentally in monkeys and found the disease to be more severe when the monkeys had been “immunised” with maternal antibodies against dengue.</p>
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<a href="https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144515/original/image-20161104-25343-rlncrl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&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">Zika and dengue can be worse after first exposure.</span>
<span class="attribution"><span class="source">from www.shutterstock.com</span></span>
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</figure>
<p>This phenomenon has implications for public health, including more serious disease outbreaks and vaccine development.</p>
<p>Could a dengue vaccine make a patient more susceptible to disease, rather than protecting them? This has been a concern for <a href="https://www.ncbi.nlm.nih.gov/pubmed/10954537">other antibody-dependent enhancement viruses</a> such as HIV, Ebola, and Ross River virus. This is why scientists first have to identify protective antibodies when proposing to use <a href="https://theconversation.com/antibody-injections-could-be-stepping-stone-to-hiv-vaccine-58858">antibody injections</a> to safeguard patients from these types of viruses.</p>
<h2>What about Zika?</h2>
<p><a href="https://theconversation.com/explainer-where-did-zika-virus-come-from-and-why-is-it-a-problem-in-brazil-53425">Zika virus</a> is a recently emerging, mosquito-borne virus that has exploded around the globe. It usually causes mild disease characterized by fever, rash and joint pain, if it causes disease at all (<a href="http://www.nejm.org/doi/full/10.1056/NEJMoa0805715#t=articleTop">about 80% of infections</a> cause no symptoms).</p>
<p>Of greater public health concern is that if a pregnant woman is infected with Zika, the virus may lead to her baby being born with a small head – a condition called <a href="https://theconversation.com/proving-that-the-zika-virus-causes-microcephaly-53716">microcephaly</a>.</p>
<p>Zika virus is a flavivirus, similar to dengue. In fact, for people infected with the virus, infection is indistinguishable from dengue using classic antibody tests. This made scientists wonder: could prior infection with Zika cause an antibody-dependent enhancement response following dengue infection or vice versa?</p>
<p><a href="http://www.pnas.org/content/113/28/7852.abstract.html?etoc">Researchers recently tested</a> whether Zika could be capable of eliciting this antibody-dependent enhancement for dengue. The findings revealed dengue antibodies can protect against Zika infection or facilitate the infection, depending on which antigens the antibodies attach to. </p>
<p>Likewise, prior Zika infection can <a href="http://science.sciencemag.org/content/early/2016/07/13/science.aaf8505?utm_campaign=fr_sci_2016-07-14&et_rid=34807079&et_cid=634260">either protect against or worsen</a> dengue infection via antibody-dependent enhancement.</p>
<h2>What does this mean for us?</h2>
<p>It doesn’t change the fact that avoiding mosquito bites is the best way of preventing disease. However, avoiding mosquito bites is easier said than done.</p>
<p>There are implications for these findings regarding the Zika vaccines under development and the future of dengue outbreaks. Developers of a Zika vaccine have to <a href="http://www.nejm.org/doi/full/10.1056/NEJMp1607762#t=article">ensure antibodies developed</a> against the vaccine will not result in antibody-dependent enhancement of dengue in the future. </p>
<p>In a region where dengue is common, such as Brazil, the recent Zika outbreak may result in more severe cases of dengue, <a href="http://science.sciencemag.org/content/early/2016/07/13/science.aaf8505?utm_campaign=fr_sci_2016-07-14&et_rid=34807079&et_cid=634260">including dengue haemorrhagic fever</a>, in the coming years.</p>
<p>Zika may have dominated the public health spotlight this year but in the coming years attention will return to dengue. As traditional mosquito control strategies lose their potency, new technologies will arise. However, the development of an affordable vaccine may be our greatest hope for reducing the burden of dengue and Zika. </p>
<p>Due to the cross-reactivity and antibody-dependent enhancement potential for these two viruses, ensuring Zika and dengue vaccines result in protective antibodies is crucial.</p><img src="https://counter.theconversation.com/content/68227/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emily Johnston Flies receives funding from The Royal Society of South Australia and the University of South Australia. </span></em></p><p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management</span></em></p>Our immune system protects us but when it comes to some mosquito-borne disease, it can work against us. What are the implications for the development of a Zika virus vaccine?Emily J Flies, PhD student in Disease Ecology, University of South AustraliaCameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/628882016-09-20T20:30:56Z2016-09-20T20:30:56ZHow can we get pharma companies to do more for global health? Try ranking them<p>The World Health Organization <a href="http://apps.who.int/medicinedocs/en/d/Js6160e/9.html#Js6160e.9">reports that a third of the world’s population</a> cannot access important medicines for some of the world’s most devastating diseases, like malaria and tuberculosis.</p>
<p>There are many reasons these drugs are out of reach of so many people, but the fact that few medicines to treat diseases like malaria and tuberculosis are developed and that the prices are high for the drugs that are developed are major factors.</p>
<p>I study ethics and work on questions about the obligations of pharmaceutical companies, and I believe that these companies have a moral and legal obligation to ensure access to essential medicines. The legal human right to health is embodied in Article 12 of the International Covenant on Economic, Social and Cultural Rights. It <a href="http://www.ohchr.org/EN/Issues/Health/Pages/SRRightHealthIndex.aspx">states that everyone has a right</a> “to the enjoyment of the highest attainable standard of physical and mental health.” This right is essential for protecting individuals’ ability to live minimally good lives.</p>
<p>When companies set high prices, lobby to extend patent protections on important medicines and do not develop enough new drugs for neglected diseases, they fail to live up to these obligations. </p>
<p>I head the Global Health Organization, which produces an index assessing the impact of drugs that treat some of the world’s most devastating diseases. As I argue in a recently <a href="http://www.ncbi.nlm.nih.gov/pubmed/27338607">published article</a> in The Journal of Law, Medicine and Ethics, this could create an incentive for companies to live up to their obligations. For instance, in the future if consumers in the developed world know which companies are doing the most for global health, they may choose to purchase products from those companies.</p>
<h2>Why are drugs so expensive?</h2>
<p>In parts of Africa and Asia about half the population cannot get the drugs that they need for diseases like malaria, tuberculosis (TB) and HIV/AIDS. This is often because these drugs are under patent and profit-driven companies can charge high prices for them even in poor countries. Moreover companies push to extend their patents through lobbying and international trade agreements.</p>
<p>For instance, delamanid, one of two new treatments for multidrug-resistant tuberculosis, must be taken with several other medicines, and the regimen can cost <a href="https://www.statnews.com/pharmalot/2016/02/25/drug-pricing-doctors-without-borders-tuberculosis/">US$1,000 to $4,500</a> for a six-month course of treatment. This is more than what <a href="http://www.un.org/en/development/desa/policy/cdp/ldc/ldc_criteria.shtml">most people make in a year</a> in many developing countries. Few developing country governments can afford the expense. </p>
<p>Companies say <a href="http://www.phrma.org/innovation/intellectual-property">patent protection is essential</a> for doing research and development on new drugs and technologies. But historical evidence suggests that patents may <a href="http://www.cambridge.org/us/academic/subjects/economics/industrial-economics/against-intellectual-monopoly?format=HB">not be a particularly effective way of promoting new research</a>. Indeed, until recently, several key innovator countries such as Italy, Germany and Switzerland had relatively weak patent protection. </p>
<h2>Why are so few essential medicines developed?</h2>
<p>The fact is that even with patents on important medicines for the world’s most widespread and devastating diseases, few are developed. Of the 1,393 medicines marketed between 1975-1999, only <a href="http://www.ncbi.nlm.nih.gov/pubmed/12090998">16 were for tropical diseases</a>.</p>
<p>The patent system on its own does not seem to be creating enough incentive to address the health problems in poor countries. Companies cannot make enough money from selling drugs to poor people in developing countries to <a href="http://www.ncbi.nlm.nih.gov/pubmed/27338607">justify the research and development expense</a>.</p>
<p>While there are many innovative <a href="http://www.ncbi.nlm.nih.gov/pubmed/14625999">strategies</a> that <a href="http://www.who.int/pmnch/topics/economics/20100505_medicinesaccessible/en/">lower the costs of existing drugs</a> and encourage the development of <a href="http://priorityreviewvoucher.org">new ones</a>, they are <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC340954/">not sufficient</a> to fully address the problem. For instance, even with increased funding for global health, from 2000-2011, only <a href="http://dx.doi.org/10.1016/S2214-109X(13)70078-0">1 percent of new chemical entities approved were for neglected disease</a>.</p>
<p>There is little reason to think we can reform the patent system to push companies to develop enough drugs for neglected diseases any time soon, but consumer action in developed countries may give companies another incentive to produce, and lower the prices on, drugs for neglected diseases. This is where the Global Health Index comes in.</p>
<h2>Supporting companies supporting the common good</h2>
<p>The Global Health Organization is supported by a <a href="http://globalcollaboration">collaboration</a> of researchers from universities and civil society organizations from around the world. We developed the Global Health Index to measure drug impact in terms of <a href="http://www.who.int/healthinfo/global_burden_disease/metrics_daly/en/">Disability Adjusted Life Years</a> saved – which incorporates both sickness averted and deaths prevented by looking at the need for the medicines, their effectiveness and access to them. </p>
<p>The index can show which drugs are making a real difference and which are not. As late as 2010, for instance, some relatively ineffective drugs for HIV/AIDS were still widely used. This is probably due to high prices for better alternatives. So, if companies lowered prices for the more effective drugs, more lives might be saved. So far, we’ve found that drugs on which Sanofi, Novartis and Pfizer held the patent had some of the largest impacts, while Eli Lilly, Kyorin and Bayer’s drugs had the smallest impacts. </p>
<p>Companies are paying attention to the index because it can <a href="http://www.marketplace.org/2015/01/23/health-care/new-effort-ranks-drugmakers-impact">affect brand perception</a>. </p>
<p>As Sanofi executive François Bompart <a href="http://www.marketplace.org/2015/01/23/health-care/new-effort-ranks-drugmakers-impact">says</a>, the Global Health Impact Index is “a good way for people to compare their performance, and… [it gives them] an incentive to do better and be more creative.” The index creates a stronger incentive for companies <a href="http://www.marketplace.org/2015/01/23/health-care/new-effort-ranks-drugmakers-impact">to be better corporate citizens</a>.</p>
<p>We plan to expand the Global Health Impact Index beyond malaria, tuberculosis and HIV/AIDS to help provide an incentive for companies to develop medicines for other neglected tropical diseases such as worms and schistosomiasis.</p>
<p>Future iterations of the Global Health Impact Index, in conjunction with other measures of corporate social responsibility like the <a href="http://www.accesstomedicineindex.org/">Access to Medicines Index</a>, might be the basis for boycotts of poorly rated companies or socially responsible investments. People could lobby insurance companies to include products from companies that perform well on the Global Health Impact Index in their formularies. </p>
<p>In the future, we envision a Global Health Impact label, like a Fair Trade label, for companies to use on all of the over-the-counter products they make – everything from pet vitamins to painkillers. The hope is that consumers in developed countries will prefer to purchase everyday medicines from companies with better rankings on the Global Health Impact Index. Similar ethical labels like “Fair Trade” have had a <a href="http://www.wageningenacademic.com/doi/book/10.3920/978-90-8686-647-2">large impact</a> in some places. </p>
<p>Millions of people suffer from devastating diseases in developing countries. By using data about what companies are doing for global health, we all might be able to push them to live up their obligations.</p><img src="https://counter.theconversation.com/content/62888/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicole Hassoun 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>In the future, consumers in the developed world could choose to purchase products from the companies that do the most to promote global health.Nicole Hassoun, Associate Professor of Philosophy, Binghamton University, State University of New YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/606742016-07-27T21:20:13Z2016-07-27T21:20:13ZGMOs lead the fight against Zika, Ebola and the next unknown pandemic<figure><img src="https://images.theconversation.com/files/132228/original/image-20160727-21595-158l7x3.jpg?ixlib=rb-1.1.0&rect=0%2C646%2C5748%2C4122&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">GMOs may very well have filled up that syringe.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-336640973/stock-photo-hand-with-a-syringe-injection-vaccination-medicine-pop-art-retro-style.html?src=pp-same_artist-346093292-5N0wHCvzYAJ7L24IKgcP_g-2&ws=1">Syringe image via www.shutterstock.com</a></span></figcaption></figure><p>The shadow of the Zika virus hangs over the Rio Olympic Games, with visitors and even <a href="http://www.telegraph.co.uk/sport/0/rio-olympics-which-athletes-have-withdrawn-over-zika-fears/">high-profile athletes citing worries</a> about Zika as a reason to stay away (even if the <a href="https://theconversation.com/the-olympics-wont-spread-zika-around-the-world-62822">risk is probably quite low</a>). The public’s concerns are a striking example of the need to rapidly combat emerging infectious diseases.</p>
<p>In the fight against <a href="https://www.cdc.gov/zika/">Zika</a>, public health experts have turned to what may sound like an unlikely ally: genetically modified organisms, or <a href="http://gmo.geneticliteracyproject.org/FAQ/what-are-gmos/">GMOs</a>.</p>
<p>Consumers are used to hearing about GMOs in food crops, but may be unaware of the vital role GMOs play in medicine. Most modern biomedical advances, especially the vaccines used to eradicate disease and protect against pandemics such as Zika, <a href="https://www.cdc.gov/vhf/ebola/">Ebola</a> and the <a href="http://www.flu.gov">flu</a>, rely on the same molecular biology tools that are used to create genetically modified organisms. To protect the public, scientists have embraced GMO technology to quickly study new health threats, manufacture enough protective vaccines, and monitor and even predict new outbreaks. </p>
<h2>Vaccines, meet molecular biology</h2>
<p>Vaccines work with the immune system to strengthen the body’s own natural defenses. A vaccine offers a preview of a potential infection, so the immune system is ready to pounce if the real threat shows up. </p>
<p>The earliest vaccines were primitive – think Edward Jenner in the 1790s <a href="http://www.jennermuseum.com/vaccination.html">inoculating against smallpox</a> by rubbing together the open wounds of uninfected patients and those with cowpox. But over the years, advances in medical technology led to improved vaccines. The modern age of vaccines was ushered in by the introduction of <a href="http://www.jove.com/science-education-database/2/basic-methods-in-cellular-and-molecular-biology">molecular biology tools</a> in the 1970s, which vastly improved our ability to study and manipulate viruses.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=513&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=513&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=513&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=644&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=644&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132067/original/image-20160726-7058-1k9brj6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=644&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Viruses have spikes for attaching to host cells and a cargo bay to hold its genes (red).</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic.mhtml?id=387259318">Virus illustration via www.shutterstock.com.</a></span>
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</figure>
<p>Under the microscope, viruses look like spiky balls, with an internal cargo bay that houses their genetic material. “Dissecting” a virus means using molecular biology tools to study its genes (whether encoded via DNA or RNA) up close. For example, researchers can “cut and paste” genes to study them in isolation and figure out what they do. Or researchers can cause genetic mutations and watch how an organism responds.</p>
<p>When DNA is modified or studied inside different cells than those from which it originated, it is called “<a href="https://www.britannica.com/science/recombinant-DNA-technology">recombinant DNA</a>.” An organism with recombinant DNA is considered a GMO.</p>
<p>GMO developers use molecular biology, manipulating genes to study and alter plant DNA, for instance, to create new varieties that can thrive with <a href="https://www.geneticliteracyproject.org/wp-content/uploads/2013/07/Biotechnology-infographic_7.29.13-clean.pdf">less water or fewer pesticides</a>.</p>
<p>For vaccine researchers, molecular biology is a jack-of-all-trades. These tools allow scientists to figure out the keys to a virus’ survival by dissecting its DNA, devise new vaccines, manufacture those vaccines cheaply and quickly, and monitor which viruses in the wild might become public health headaches. According to <a href="http://medschool.umaryland.edu/FACULTYRESEARCHPROFILE/viewprofile.aspx?id=25096">Dr. José Esparza</a>, president of the <a href="http://gvn.org/">Global Virus Network</a> and professor at University of Maryland Medical School, “It is impossible to do research in biomedicine without doing molecular biology.”</p>
<h2>GMOs advance science of vaccines</h2>
<p>One disease currently being addressed with the help of molecular biology is <a href="http://www.who.int/mediacentre/factsheets/fs204/en/">hepatitis B</a>, which kills one person every minute worldwide – even though we do have an effective vaccine.</p>
<p>In the 1960s, virologists realized that the hepatitis B antigen – a protein from the virus’ outer shell that triggers an immune response in an infected person – showed up in the blood of hepatitis B patients. To their surprise, injecting a healthy person with the purified antigen protected against future infections. The first hepatitis B vaccine (<a href="http://www.nasonline.org/publications/beyond-discovery/hepatitis-b-story.pdf">HBV</a>), approved in 1981, was made by harvesting the antigen from the blood of hepatitis B carriers, including intravenous drug users.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132201/original/image-20160727-21591-273uhb.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">Administering the hepatitis B vaccine to a child at a rural health center in India.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/unitednationsdevelopmentprogramme/4968223306">United Nations Development Programme</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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</figure>
<p>Once recombinant DNA technology was developed, researchers could isolate the gene for the virus’ antigen protein, allowing for HBV to be manufactured in laboratories via those genetic instructions instead of from infected blood. Currently, both FDA-approved <a href="https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/appdx-full-b.pdf">vaccines for hepatitis B</a> include the recombinant version of the antigen. </p>
<p>And molecular biology can be used to accelerate the development of new vaccines. For example, in late June, a “<a href="https://www.statnews.com/2016/06/20/zika-vaccine-inovio/">DNA vaccine</a>” was the first to be approved for human trials against the Zika virus. Rather than containing the Zika antigen itself, the vaccine contains a gene for the Zika antigen which the patient’s body then produces.</p>
<p>The announcement of this breakthrough came less than five months after the World Health Organization declared Zika a “<a href="http://www.who.int/mediacentre/news/statements/2016/emergency-committee-zika-microcephaly/en/">public health emergency of international concern</a>.” Without the tools to modify and isolate sections of DNA, Dr. Esparza of the Global Virus Network notes, “we would not be able to do this with the necessary speed and efficiency.”</p>
<h2>GMOs as pharma factories</h2>
<p>Consumers who scrupulously avoid genetically modified foods might be surprised to know that lots of <a href="https://gmoanswers.com/studies/gmos-food-and-medicine-overview">drugs and vaccines</a> they rely on are the product of GMOs.</p>
<p>Many vaccines and top-grossing pharmaceuticals contain proteins as the main ingredient. Proteins are <a href="http://dx.doi.org/10.3389/fmicb.2014.00172">too costly</a> and delicate to manufacture from scratch. But living cells must make proteins to survive, and they can be coaxed to produce medical proteins in bulk, requiring little more than the DNA instructions and sugary broth as fuel. Since these genetic blueprints must be inserted into the cells, many vaccines and drugs are technically the product of GMOs. </p>
<p>Modified bacteria, yeast and even <a href="https://biotechhistory.org/magazine-article/vital-tools-brief-history-cho-cells/">Chinese hamster cells</a> are the unheralded molecular factories of the drug and vaccine industry. In 2014, 10 of the <a href="http://cellculturedish.com/2015/03/10-biologics-on-best-selling-drugs-list-for-2014/">top 25 best-selling drugs</a> were “<a href="http://www.fda.gov/AboutFDA/CentersOffices/OfficeofMedicalProductsandTobacco/CBER/ucm133077.htm">biologics</a>” – drugs made up of recombinantly produced proteins – including blockbuster treatments for arthritis, cancer and diabetes. Of the 10 vaccines that the <a href="https://www.cdc.gov/vaccines/parents/downloads/parent-ver-sch-0-6yrs.pdf">Centers for Disease Control and Prevention (CDC) recommends</a> for newborns, three are available in recombinant form; HBV, for example, is produced by modified yeast. The earliest recombinant vaccines and drugs have been in use for <a href="http://www.biotechnology.amgen.com/timeline.html">three decades</a>. </p>
<p>Perhaps the most dramatic example of GMO use in medicine came during the 2014 Ebola outbreak in West Africa. When American doctor Kent Brantly and other Western volunteers contracted Ebola, several were cured by a “<a href="http://wgntv.com/2014/08/04/secret-serum-likely-saved-ebola-patients/">secret serum</a>” called <a href="http://doi.org/10.1038/nature13777">Zmapp</a>. Manufactured by <a href="http://www.fastcompany.com/3045741/most-creative-people-2015/meet-ebolas-soft-spoken-plant-loving-arch-nemesis">genetically modified tobacco plants</a>, it’s a mixture of several proteins that attack the Ebola virus.</p>
<p>The technology for producing drugs in genetically modified plants, dubbed “pharming,” was developed by <a href="https://sols.asu.edu/people/charles-arntzen">Charles Arntzen</a> in the early 1990s. In the case of Zmapp, the antibodies are made in the tobacco plant’s leaves. When they’re harvested, rather than being made into cigarettes, their cells are popped open and the drug is collected. Researchers call pharming “<a href="http://www.fastcompany.com/3045741/most-creative-people-2015/meet-ebolas-soft-spoken-plant-loving-arch-nemesis">a revolution for the field</a>” of manufacturing pharmaceuticals.</p>
<p>The biotech company <a href="http://www.appliedbiotech.org">Applied Biotechnology Institute</a> has embraced the technique to make a next-generation pharmed vaccine. They’re developing a genetically modified corn plant that produces the hepatitis B antigen. The plant could be harvested and turned into an oral vaccine tablet, which looks like a small wafer, as opposed to a liquid which must be refrigerated and injected. The hope is that an oral vaccine can lower the rates of hepatitis B in the developing world, where the cold supply chain, sanitary needles and trained medical personnel the current vaccine depends on are either lacking or prohibitively expensive.</p>
<h2>Future of diagnostics</h2>
<p>Beyond improved vaccines, equally pressing for the future of public health will be addressing pandemics that have not yet even begun. Virologist Esparza counts 11 pandemics that have occurred in the last 14 years, including Ebola, the <a href="http://www.flu.gov/about_the_flu/h1n1/">H1N1 (swine) flu</a> and <a href="https://www.cdc.gov/coronavirus/mers/">MERS</a> – all but one of which were viruses. “It is totally predictable there will be other pandemics. What is not easy to predict is which one. Two years ago, no one could have predicted Zika,” he told me.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132267/original/image-20160727-21578-1cb427x.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>
<figcaption>
<span class="caption">Molecular biology technology has made possible simple diagnostic tools, like this paper-based test for Zika. Areas that have turned purple indicate samples infected with the virus.</span>
<span class="attribution"><span class="source">Wyss Institute at Harvard University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p>Molecular biology is often found on the front lines of pandemics, appearing in on-the-spot diagnostic tools that are cheap and do not require extensive equipment or training. For example, a Harvard-led team <a href="http://dx.doi.org/10.1016/j.cell.2016.04.059">recently unveiled</a> a <a href="http://www.forbes.com/sites/jenniferhicks/2016/05/09/researchers-develop-low-cost-paper-diagnostic-test-for-zika-virus/#24ee99f53fb4">paper-based test</a> – similar to a pregnancy test – that uses the <a href="https://theconversation.com/crispr-cas-gene-editing-technique-holds-great-promise-but-research-moratorium-makes-sense-pending-further-study-43371">CRISPR/Cas</a> gene editing tool to distinguish the Zika virus from the closely related <a href="https://www.statnews.com/2016/02/17/zika-dengue-infections/">Dengue virus</a>. If the Cas9 protein encounters the specific DNA sequence of Zika virus in a drop of blood, it starts a chain reaction that results in a colored readout.</p>
<p>Beyond diagnosing single patients, molecular biology tools will be used to get ahead of the as-yet-unknown pandemic threats that lie in the future. Public health officials are <a href="http://www.who.int/csr/alertresponse/en/">calling for monitoring infections</a> in the places where new diseases frequently emerge. Quick and accurate diagnostic tests are key to determining which viruses are already circulating and would allow researchers to anticipate new pandemics and develop and stockpile vaccines. </p>
<p>“Until now, we have had a very reactive response” to threats like Zika and Ebola, says Dr. Esparza. With the help of GMOs, infectious disease experts have the tools to get ahead of the next outbreak, moving beyond reaction to quick detection, containment and even prevention.</p><img src="https://counter.theconversation.com/content/60674/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeff Bessen works in a molecular biology lab that has received funding on various projects from the NIH, HHMI, and DARPA. The lab has received funding from Monsanto for a project unrelated to vaccines and medicines.
</span></em></p>Public health experts enlist the molecular biology tools that create genetically modified organisms – as well as the GMOs themselves – in the fight against emerging infectious diseases.Jeff Bessen, Ph.D. Candidate in Chemical Biology, Harvard UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/628162016-07-22T03:27:34Z2016-07-22T03:27:34ZIs the end of Zika nigh? How populations develop immunity<p>The Zika outbreak, arriving on the heels of Ebola and just in time for the Rio Olympics, has challenged global health agencies to respond rapidly and effectively. Determining the appropriate response is far from straightforward, though, as there is much we don’t yet know about the Zika virus.</p>
<p>A <a href="http://science.sciencemag.org/content/early/2016/07/13/science.aaf8160">pair</a> of <a href="http://science.sciencemag.org/content/early/2016/07/13/science.aag0219">papers</a> published recently in the journal Science have reviewed current evidence about the spread and control of Zika. These studies use mathematical models to help understand how the virus may spread. Insights from these models can help to prioritise efforts to control Zika and minimise the harm it causes.</p>
<p>One conclusion from these models is that little can be done to contain the current Zika outbreak in South America. Vaccines are <a href="http://www.nature.com/nature/journal/vaap/ncurrent/full/nature18952.html">under development</a>, but may arrive too late to have a substantial impact on this outbreak. <a href="http://www.who.int/emergencies/zika-virus/articles/mosquito-control/en/">Long-term control</a> of the mosquitos that transmit Zika, among other diseases, remains an ongoing challenge.</p>
<p>Despite this, the models suggest the outbreak will die out of its own accord in around three years from now. After that we may not see further outbreaks for at least a decade. </p>
<h2>How do populations become immune?</h2>
<p>When we are exposed to a pathogen, our body produces an immune response to defend itself. This immune response not only clears the pathogen, but often provides protection against further infection even after we recover, so we’re not susceptible to being infected again.</p>
<p>Infectious diseases spread when a pathogen (a virus, bacteria or parasite) is transmitted from an infectious person to a person who is susceptible to infection. During an outbreak, lots of people can become infected in a short time and develop immunity.</p>
<p>As a result, the number of susceptible people left available to be infected is reduced, making it harder for the pathogen to keep spreading. The number of new infections declines and the outbreak ends, without it being necessary for everyone to have been infected. The current models suggest this will occur with the Zika outbreak over the coming years.</p>
<p>After a large outbreak has run its course, there may no longer be enough susceptible people in a population to allow a further outbreak to occur. Even if an infectious person enters this population, most people they meet will be protected, due to past exposure, and the disease won’t be able to spread very far. This inability for the pathogen to spread then provides indirect protection for those who remain susceptible. This population-level phenomenon of protection is known as “<a href="https://theconversation.com/explainer-what-is-herd-immunity-52377">herd immunity</a>”.</p>
<p>While we usually aim to achieve herd immunity through vaccination, in the case of Zika the models predict that herd immunity will be achieved through natural infection.</p>
<h2>So how could Zika ever return?</h2>
<p>There are two ways a population can become “outbreak-ready” again. First, people who have recovered from infection may eventually lose the protection gained from their immune response and become susceptible again. </p>
<p>How long this protection lasts varies from disease to disease. For some diseases, such as chlamydia, it may be very short-lived or even non-existent. For others, such as measles, protection may be near lifelong.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=764&fit=crop&dpr=1 600w, https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=764&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=764&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=960&fit=crop&dpr=1 754w, https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=960&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/131343/original/image-20160721-8642-zljgpb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=960&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">Protection against measles is near lifelong, which is why most outbreaks have historically occurred in children.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/perpetualplum/3796080398/">Sue Clark/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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</figure>
<p>Second, infants are typically susceptible to disease when they are born. Over many years, the birth of enough susceptible infants may create the conditions for a new outbreak to occur. </p>
<p>This is why, before the development of vaccines, measles outbreaks tended to occur every two to three years, predominantly involving young children. During an outbreak, almost all of the susceptible people in a population would be infected. It would then take two or three years for enough children to be born to provide enough susceptible people for a further outbreak.</p>
<p>The first outbreak of a disease in a new population, as we are observing with Zika in Latin America, is a special case. Because few people in the population are likely to have immunity from prior exposure, there will be more susceptible people and the outbreak will be much larger. We might then expect an even longer gap before the next outbreak.</p>
<h2>Planning ahead</h2>
<p>We don’t know how long people are protected after being infected with Zika virus. Comparison with other similar viruses suggests <a href="http://www.who.int/mediacentre/factsheets/fs117/en/">immunity might be lifelong</a>. If this is the case, the expected time before another outbreak can be estimated by considering how long it will take for enough newly susceptible people to be born. The Science article estimates this to be at least ten years based on currently available data.</p>
<p>Many other factors can influence the waiting time between outbreaks. <a href="http://www.sciencedirect.com/science/article/pii/S1931312816301421">Changes in the genetic structure</a> of the Zika virus may lead to a more rapid loss of herd immunity. Geographic variation in the spread of disease could leave some populations relatively unaffected and vulnerable to outbreaks. </p>
<p>If climatic change extends the range of disease-bearing mosquitoes, <a href="http://www.who.int/globalchange/climate/summary/en/index5.html">new susceptible populations</a> may be exposed to Zika. Changes in population demography and behaviour may also <a href="http://wwwnc.cdc.gov/eid/article/1/1/95-0102_article">affect the epidemic dynamics</a>.</p>
<p>Mathematical models such as the one used in the Science study enable exploration of many scenarios, helping to make sense of <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4445966/">how these factors interact</a>. By testing out alternative outbreak response strategies, models can inform decisions about which interventions will most effectively minimise harm. Models also enable us to quantify our uncertainty about which future course of events will come to pass.</p>
<p>Importantly, these models also show researchers where the most important gaps in our knowledge are. In the case of Zika, these studies identify an urgent need for better data on who has been infected in the past, not only in Latin America, but also in other regions that may be at risk, such as Asia. </p>
<p>This is challenging because many people infected with Zika virus will not become sick. Those who do may experience symptoms that could be mistaken for those caused by other diseases such as dengue or chikungunya. Better diagnostic tests are needed to estimate the current level of herd immunity to Zika in different populations and identify those most at risk.</p><img src="https://counter.theconversation.com/content/62816/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Geard receives funding from the National Health and Medical Research Council and the Australian Research Council. </span></em></p><p class="fine-print"><em><span>James McCaw receives funding from the National Health and Medical Research Council, Australian Research Council, Commonwealth Department of Health and Defence Science Technology Group that supports his research on infectious diseases.</span></em></p><p class="fine-print"><em><span>James Wood receives funding from the NHRMC through the PRISM CRE, and project grants in relation to tuberculosis and pneumococcal disease and from UNSW in relation to pertussis. </span></em></p><p class="fine-print"><em><span>Jodie McVernon receives funding from the National Health and Medical Research Council, including through the Centres of Research Excellence in Infectious Diseases Modelling to Inform Policy (PRISM) and the Australian Partnership for Preparedness Research on Infectious Disease Emergencies (APPRISE) </span></em></p><p class="fine-print"><em><span>Cameron Simmons 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>During a disease outbreak, lots of people can become infected in a short time and develop immunity, making it hard for the pathogen to spread.Nic Geard, ARC DECRA Research Fellow, Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneCameron Simmons, Laboratory Head, Department of Microbiology and Immunology, The University of MelbourneJames McCaw, Associate Professor in Mathematical Biology, The University of MelbourneJames Wood, Public health academic, UNSW SydneyJodie McVernon, Professor and Director of Doherty Epidemiology, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/618102016-07-07T02:26:34Z2016-07-07T02:26:34ZNews of Zika vaccine might be reassuring, but it’s too late for Rio, and do we really need it anyway?<p>Recently, two events concerning the Zika epidemic coincided: two potential vaccines against the virus were <a href="http://www.nature.com/nature/journal/vaap/ncurrent/full/nature18952.html#main">declared a success</a> when used in mice, and Australian golfer <a href="http://www.abc.net.au/news/2016-06-29/jason-day-hopes-golf-stays-in-the-olympics-despite-rio-withdraw/7552788">Jason Day withdrew</a> from the Olympic Games, purportedly because of his concern about the possibility of getting infected. </p>
<p>The number of media reports of these events highlight the sensationalism around Zika and the challenges faced by scientists and public health professionals in translating science to policy.</p>
<p>Zika captured global public attention partly through the spectacle of the birth deformities it has been linked to, particularly <a href="https://theconversation.com/explainer-what-is-microcephaly-and-what-is-its-relationship-to-zika-virus-54049">microcephaly</a> and <a href="https://theconversation.com/explainer-what-is-guillain-barre-syndrome-and-is-it-caused-by-the-zika-virus-53884">other neurological disorders</a>, but partly also because of the Olympic Games. Without the economics of international sport, the virus may well have been ignored.</p>
<p>Zika was first identified in humans in Uganda some 70 years ago. By early July 2016, the current epidemic was prevalent throughout the Americas and in Asia and the Western Pacific region.</p>
<p>It is a comparatively benign virus: many people do not know they are infected, in contrast with other viruses in the same family (flaviviruses). Yellow fever is now largely controlled through vaccination and medical surveillance. Dengue fever and dengue haemorrhagic fever, and chikungyna are virulent, but are considered neglected diseases of poverty. </p>
<p>The diseases affect poor people in poor countries with limited capacity to manage the environment, control the carrier, or provide accessible and affordable health care.</p>
<p>Zika virus infection was <a href="https://theconversation.com/zika-emergency-status-a-cause-for-alert-not-alarm-54042">declared a public health emergency</a> of international concern in February 2016. This followed an increase in infections in Brazil and its suspected link with congenital anomalies. The number of people who have contracted the Zika virus is imprecise – in part because those who are infected may have no obvious signs, compared with the more deadly flaviviruses – dengue fever, chikungunya and yellow fever. </p>
<p>All are transmitted by the mosquito species <em>Aedes aegypti</em> and <em>Aedes albopictus</em>. The prevalence of these species varies with topography, precipitation, population density, the management of hard waste, and the built environment.</p>
<h2>What do we know about the vaccine so far?</h2>
<p>The <a href="http://www.nature.com/nature/journal/vaap/ncurrent/full/nature18952.html#main">success of two novel vaccines</a> against Zika in mice is a remarkable achievement, especially given the lack of vaccines against dengue and chikungunya. But the roll-out of either of these vaccines is too far off to impact the Olympic Games. </p>
<p>We know nothing of the efficacy of the vaccines in the short or long term; their effect on people who have already been infected or are subsequently exposed to other flaviviruses; or their effect on women in pregnancy. Is the vaccine stable in varying temperatures? How resistant is the vaccine to mutation of the virus? How long before the vaccine ceases to be effective?</p>
<p>The next step for the vaccines is to conduct clinical trials in humans. These are usually conducted among poor populations in poor countries not only because of the greater prevalence of the targeted infection, but also because it can be easier to get past their ethics committees to conduct the studies.</p>
<p>Assuming the vaccine is successful, then globally and at country levels we will need to address health systems and service problems. </p>
<p>Who should receive the vaccine, and at what cost? If it is not free, then the vaccine will likely only protect people who are at low risk (tourists, for instance). If it is provided free to poor countries where health systems are weak, then who will cover the high cost of the vaccine roll-out, procurement, storage, local distribution, community education and monitoring across populations?</p>
<h2>So what about Rio?</h2>
<p>While Zika has been reported in around 60 countries, almost all of the <a href="http://www.who.int/emergencies/zika-virus/situation-report/23-june-2016/en/">1,655 cases of microcephaly confirmed by WHO</a> (as at June 22) have occurred in Brazil. The vast majority of these have been in the impoverished states of Pernambuco and Paraiba, over 1,600 kilometres northeast of Rio.</p>
<p>The concentration of cases in this region, predating the rise in the transmission of Zika, has yet to be explained. And only a small proportion of these cases of microcephaly <a href="http://www.paho.org/hq/index.php?_option=com_content&view=article&id=11599:regional-zika-epidemiological-update-americas&Itemid=41691&lang=en">have been shown to be linked to Zika</a>.</p>
<p>The mosquito carrier, or “vector”, is active in Rio de Janeiro, but biting rates are low in August – the month of the Olympics. This means the risk of any disease transmitted by <em>Aedes</em> mosquitoes during the Games will be low. The vector is not especially efficient in transmitting Zika as it’s harder to transmit than some other viruses.</p>
<p>The risk of infection through sex is <a href="https://theconversation.com/zika-via-sex-and-blood-how-worried-should-we-be-54174">infinitely lower</a>: the promotion of so-called <a href="https://theconversation.com/antiviral-condoms-will-help-protect-australian-olympians-from-stis-heres-how-59467">“Zika-proof” condoms</a> (special HIV-proof condoms have not been marketed) is an extraordinary example of capitalising on fear.</p>
<p>Sex and birth deformities make news, and so do medical breakthroughs. Mosquito control rarely does. Mosquito control for Zika is difficult, because <em>Aedes aegypti</em> prefers to graze on humans at dawn, late afternoon and early evenings; it is therefore perfectly adapted to spread any virus. </p>
<p>Images in the media of militarised mosquito-control programs evoke the successful campaigns against the same vectors in the Americas from the 1920s to 1950s to fight yellow fever, But fogging and spraying breeding sites is expensive and requires quick action before the vector develops insecticide resistance and so outwits the strategy. </p>
<p>The most effective intervention is to prevent exposure by reducing breeding sites in urban areas – getting rid of old spare tyres, removing water in the saucers of houseplants, and so on – and by humans reducing the likelihood of being bitten through wearing protective clothing and mosquito repellent. So rather than avoiding Rio, we can probably follow the logic of the epidemiology and take the risk.</p>
<img src="https://counter.theconversation.com/content/61810/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lenore Manderson 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>Recently two events concerning the Zika epidemic coincided: two potential vaccines against the virus were declared a success when used in mice, and Jason Day withdrew from the Olympic Games.Lenore Manderson, Visiting Distinguished Professor of Environmental Studies, Brown University, USA, and Distinguished Professor, Public Health and Medical Anthropology, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.