On 23rd August 2021, WHO Director-General Tedros Adhanom called for a two-month moratorium on COVID booster vaccines, believing that vaccine doses should be saved for less developed countries. Largely symbolic and lacking legal enforceability, the call was but a plea from a leader who has seen his calls for greater equitability in vaccine distribution being ignored. Various countries such as Israel and the United States have already begun administering booster doses, while many others plan to do so in the near future. After a long two years living with a pandemic, and just as the initial vaccines seemed to provide a path to normality, we tackle a burning question: to boost or not to boost.

Let us first begin by introducing the concept of a booster. A booster shot, such as for Hepatitis B, is an additional dose of vaccine administered some time after the initial immunisation, designed to trigger the body’s immune response once again and further strengthen it, either because the initial dosage was insufficient or immunity has waned. Most COVID vaccines administered today are either mRNA vaccines (such as Pfizer’s and Moderna’s), which provide your body with the instructions to manufacture harmless parts of the virus, and vector vaccines, (such as AstraZeneca’s) which delivers similar harmless viral parts, ‘ready-made’, into your body. In both cases, the body mounts an immune response against these viral parts and develops long term immunity in terms of antibodies and memory T-cells circulating in the blood, ready to deal with any COVID virus which attempts to infect cells in the body.

So, to boost or not to boost? The answer lies in balancing the pros and cons. Both are certainly present — there is the benefit of a third exposure to the viral antigen, and there are, of course, risks, as with any vaccine. Data seems to suggest a fall of 14% (to 74%) after 5-6 months for Pfizer and 10% (to 67%) for AstraZeneca. Pfizer restores to 95% upon a booster. However, older and immunocompromised individuals have weaker immune systems; both their initial and subsequent immunity is expected to be less. The mRNA vaccines seem to cause, in rare instances, inflammation of the pericardium around the heart and, with AstraZeneca, unusual blood clots with low platelet counts. This, and the opportunity cost of not giving the vaccine to the rest of the world who needs it, is why most countries still seem hesitant on giving a booster to the rest of the population. Unsurprisingly, data is limited for immunocompromised individuals since they received their initial doses later — we will only know for certain if their immunity wanes significantly in time to come. For now, it seems that the benefit does outweigh the cost in older individuals and the immunocompromised, but the jury is still out on the rest of the population.

“The initial vaccines seemed to provide a path to normality”

Science and medicine aside, there is yet an important aspect to this discussion — i.e. the equitability or fairness of administering third doses in certain countries while others have yet to even get first doses to many of their people. The scientists agree — the marginal benefit of a first dose far outweighs that of a third one. However, it is not science that is the issue but politics. What we see here is a clash between the interests of nation-states and the global collective. So long as governments see a benefit in booster shots nationally, it is more politically expedient for them to oppose donating vaccines to the global community.

The solution to a political problem should also be political — perhaps it’s not so much about competing for a fixed supply, but other issues such as distribution, manpower, public trust in vaccine efficacy or incentivising greater production by relaxing patent laws. That, however, is a discussion for another day.

Yet another plausible scenario is that we see an annually seasonal shot to handle new variants that emerge, such as the flu vaccine, which differs year on year to reflect the prevailing variants. Given that the rate of mutation of COVID seems to be less than the flu, it is too early to say for sure. Moreover, a one-size-fits-all approach may not work. With our current hindsight, close monitoring of potentially ‘vaccine busting’ variants would allow their spread to be contained to a single locality, and vaccines specific to these variants may be administered to individuals living there.

“The solution to a political problem should also be political”

All in all, as cliché as it may seem, we won’t know what we need until we have more data. A wide range of factors can affect whether we need the booster, including the composition of variants in an area, the prevalence of COVID and number of vulnerable individuals, and last but certainly not least — the elephant in the room — the cost of purchasing and administering the vaccine. With vaccines, we see a clash of individual and collective interests; the benefit to a nation may or may not be greater than the cost. The WHO Director-General’s call for a moratorium on boosters certainly has the backing of science — in that despite the benefits of boosters for individuals, shots are far better off administered to the currently unvaccinated; whether he has the political power to convince wealthy countries of this fact is another question altogether.