COVID-19: Who should get a vaccine first?
The Fair Priority Model is a three-phase plan for vaccine distribution.
There are currently a number of potential coronavirus vaccines being researched. But once a successful one has been developed, it is likely to be in short supply. So how do we decide who to allocate the vaccines to, and how to distribute them across countries?
A team of global health experts have proposed a new, three-phase plan for vaccine distribution that aims to mitigate future adverse effects of COVID-19, which they call the ‘Fair Priority Model’.
Phase 1 aims to prevent deaths – especially premature death – and other irreversible health impacts. Phase 2 continues addressing health concerns, but also aims to reduce economic and social impacts, like closures of schools and businesses. Phase 3 aims at lowering community transmission, which will also reduce spread between countries.
At each phase, a certain number of vaccines would be allocated to each country, depending on where it would have the greatest impact. For example, in phase 2, priority would be given to countries where vaccines would reduce more poverty and avert the most lost income per dose.
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The researchers argue that the Fair Priority Model is more equal than other current proposals, as it responds more appropriately to the needs of different countries. This is necessary, as equally populous countries are facing dramatically different levels of death and economic devastation from the pandemic.
In contrast, current proposals from experts say that countries with large numbers of health care workers and over-65s should receive immunisation first, or that countries should receive doses proportional to their population.
“The idea of distributing vaccines by population appears to be an equitable strategy,” said Dr Ezekiel J. Emanuel, who led the research. “But the fact is that normally, we distribute things based on how severe there is suffering in a given place, and, in this case, we argue that the primary measure of suffering ought to be the number of premature deaths that a vaccine would prevent.”
How do scientists develop vaccines for new viruses?Vaccines work by fooling our bodies into thinking that we’ve been infected by a virus. Our body mounts an immune response, and builds a memory of that virus which will enable us to fight it in the future.
Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been ‘killed’, but which still activate the immune system), and attenuated vaccines (which use live viruses that have been modified so that they trigger an immune response without causing us harm).
A more recent development is recombinant vaccines, which involve genetically engineering a less harmful virus so that it includes a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.
Over the past few years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against the Ebola virus. It consists of a vesicular stomatitis animal virus (which causes flu-like symptoms in humans), engineered to have an outer protein of the Zaire strain of Ebola.
Vaccines go through a huge amount of testing to check that they are safe and effective, whether there are any side effects, and what dosage levels are suitable. It usually takes years before a vaccine is commercially available.
Sometimes this is too long, and the new Ebola vaccine is being administered under ‘compassionate use’ terms: it has yet to complete all its formal testing and paperwork, but has been shown to be safe and effective. Something similar may be possible if one of the many groups around the world working on a vaccine for the new strain of coronavirus (SARS-CoV-2) is successful.