Review Panel: Scientific Evidence Does Not Support Booster Doses

Even with the Delta variant as the predominant strain now, a group scientists concluded that vaccine efficacy against severe COVID-19 is so high that booster doses for the general population are not appropriate at this stage in the pandemic.

A group of scientists has come out against booster doses after reviewing the current data from randomized controlled trials and observational studies. The scientists included people from the World Health Organization (WHO) and the Food Drug Administration (FDA).

Their review, published in The Lancet, summarizes the currently available evidence published in peer-reviewed journals and pre-print servers.

“The vaccines that are currently available are safe, effective, and save lives. Although the idea of further reducing the number of COVID-19 cases by enhancing immunity in vaccinated people is appealing, any decision to do so should be evidence-based and consider the benefits and risks for individuals and society. These high-stakes decisions should be based on robust evidence and international scientific discussion,” co-author Soumya Swaminathan, MBBS, MD, chief scientist WHO, said.

A chief concern raised by the panel was the idea that for those who have been vaccinated they are afforded a much higher level of protection than those who are unvaccinated and this latter group should get access to the initial doses of the vaccines.

“Taken as a whole, the currently available studies do not provide credible evidence of substantially declining protection against severe disease, which is the primary goal of vaccination,” lead author Ana-Maria Henao-Restrepo, MD, medical officer at the Initiative for Vaccine Research (IVR), Department of Immunization Vaccines and Biologicals, WHO, said. “The limited supply of these vaccines will save the most lives if made available to people who are at appreciable risk of serious disease and have not yet received any vaccine. Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated. If vaccines are deployed where they would do the most good, they could hasten the end of the pandemic by inhibiting further evolution of variants.”

Back in early August, WHO’s Director General Tedros Adhanom Ghebreyesus PhD, had requested a moratorium on all COVID-19 booster vaccine shots including high-risk populations such as health-care workers and the elderly—at least through September.

He said he would like to see other countries who have not had access to even the first doses of the vaccines get an opportunity.

“We cannot and should not accept countries that have already used most of the global supply of vaccines using even more of it while the world’s most vulnerable people remain unprotected,” WHO Adhanom Ghebreyesus said at the time.

The authors in The Lancet article note that even if levels of antibodies in vaccinated individuals wane over time, this does not necessarily predict reductions in the efficacy of vaccines against severe disease. This could be because protection against severe disease is mediated not only by antibody responses, which might be relatively short lived for some vaccines, but also by memory responses and cell-mediated immunity, which are generally longer-lived. If boosters are ultimately to be used, there will be a need to identify specific circumstances where the benefits outweigh the risks.

They also had concerns about the messaging of booster doses might have on people's beliefs on the vaccines overall.

“The message that boosting might soon be needed, if not justified by robust data and analysis, could adversely affect confidence in vaccines and undermine messaging about the value of primary vaccination,” the authors wrote in the review.