COVID-19 booster shot: Why it is not an appropriate strategy to adopt right now

The expert review, which was accessed by Financial Express Online, included scientists from the international community, including those from the WHO and the FDA.

COVID-19 Booster shot: While several people around the world are speculating about booster shots, an expert review published in The Lancet Journal has concluded that giving booster shots to the general population at this stage is not appropriate. This, the paper said, is because even for the Delta variant, the vaccine is very effective against severe COVID-19 infection. The expert review, which was accessed by Financial Express Online, included scientists from the international community, including those from the WHO and the FDA. The review is based on the evidence from randomised controlled trials that are currently available and the observational studies published in journals and on pre-print servers.

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The review said that one of the consistent findings from the observational studies was the high efficacy that vaccines continued to demonstrate against severe infections – be it from the delta variant or the alpha variant. It was also found that the vaccines were more than 80% effective in providing protection against any infection at all caused by these variants.

Moreover, it was also stated that across all the variants of the virus and all of the types of vaccines, the vaccines were found to be more effective against severe disease as compared to mild disease. The review also clearly stated that even though in comparison the vaccines were less effective against asymptomatic cases or against virus transmission than severe disease, it was found that even in populations where vaccination administration rates were high, it was the unvaccinated minority of people that were found to be majorly driving the transmission of the virus, and it was this minority itself that was at the highest risk of contracting severe infection.

Lead author of the paper, WHO’s Dr Ana-Maria Henao-Restrepo said that the main goal of the vaccination was to provide significant protection against severe infection and added that at present there was no evidence that this protection was significantly declining. Hence, noted Dr Ana-Maria, that the limited supply of vaccine would be put to better use if it were redirected to people who are vulnerable to the disease and have not yet been vaccinated. The lead author also added that even if booster shots were to add some gain in protection, its benefits would still not outweigh those that would be received from routing vaccine doses towards increasing initial protection. This, Dr Ana-Maria said, would do the most benefit since it would lead to a larger population being vaccinated and therefore, would inhibit the evolution of more variants.

The review authors also noted that a decline in the levels of antibodies also did not necessarily imply a decreased vaccine efficacy against the disease, because antibodies responses are not the only factor providing protection against a severe disease. The experts noted that antibody responses can be relatively short-lived, but protection against the disease can also be mediated by memory responses and cell immunity, which generally live longer.

It was also noted that since vaccines are currently producing highly effective response to the current variants, it means that the virus has not yet evolved to the point where they have started escaping the immune response. Moreover, any further variants that are likely to evolve would come from the strains that are already widely prevalent, and therefore, booster shots that would be developed specifically to tackle the newer potential variants would be more effective in fighting the infections that result from them, instead of another shot of the current vaccine itself.