Boosters Are ‘Not Appropriate’ – Reach Unvaccinated First  

The current COVID-19 vaccines are effective enough against severe disease in the general population that boosters are “not appropriate” even for the Delta variant, according to an expert review by an international group of scientists from the World Health Organization (WHO), the US Food and Drug Administration (FDA) and international universities.

The review, which looked at current evidence from randomised controlled trials and observational studies published in peer-reviewed journals and pre-print servers, was published in The Lancet on Monday.

“Averaging the results reported from the observational studies, vaccination had 95% efficacy against severe disease both from the Delta variant and from the Alpha variant, and over 80% efficacy at protecting against any infection from these variants. Across all vaccine types and variants, vaccine efficacy is greater against severe disease than against mild disease,” according to a press release from The Lancet.

The “Viewpoint” article, led by Dr Philip Krause, of the United States Food and Drug Administration’s Offices of Vaccines Research and Review, and including a number of senior WHO scientists, concluded that results reported from the observational studies it had reviewed, vaccination had 95% efficacy against severe disease both from the delta variant and from the alpha variant, and over 80% efficacy at protecting against any infection from these variants. 

“Current evidence does not, therefore, appear to show a need for boosting in the general population, in which efficacy against severe disease remains high,” concluded the 18 authors, including Dr Ana-Maria Henao-Restrepo, WHO’s Head of Research and Development, Soumya Swaminathan, WHO Chief Scientist, and Mike Ryan, executive director of WHO Emergencies.

 “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,” said Henao-Restrepo, in a press release.

Authors admit data is ‘partial’

The article is based upon a review of nearly two dozen studies that looked at hospitalisation rates among vaccinated people, immune response to the vaccines in the laboratory and among clinical populations over time, and also studies on responses to the brand-new booster shots.

The authors also admit that the data is partial, and changing. 

That’s underlined by the fact that while the review included one paper on initial findings from Israel’s booster programme – one of the first in the world, it failed to note the results cited there, which found a 10-fold decrease in the relative risk of severe illness among people receiving the booster shot 12 days after receiving it, within a cohort of over 1.14 million vaccinated individuals, aged 60 and over. 

Even more recent data from Israel, which has called itself the “world’s laboratory” on vaccine boosters, reflects a stabilisation of infection rates and decline in hospitalised cases as the country experienced the highest infection surges, per capita, in the world. That decline has helped avert a crisis in intensive care and another lockdown, experts say, and can only be attributed to the aggressive administration of booster vaccines – which have now been administered to over one-quarter of the population.,


Restating positions already articulated by WHO publicly, the authors argue that instead of administering additional vaccines to people who have already been vaccinated, reaching the unvaccinated is the most important public health imperative as they are both the major drivers of transmission and at the highest risk of serious disease, according to the authors. 

“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,” added Henao-Restrepo, in the press release.  

Another argument for avoiding boosters right now, she said, is to enable wider vaccine distribution worldwide, so as to hinder the development of dangerous variants. 

“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.” 

Boosting ‘might ultimately be needed’

The authors acknowledge that in the “changing situation” that “boosting might ultimately be needed in the general population because of waning immunity to the primary vaccination or because variants expressing new antigens have evolved to the point at which immune responses to the original vaccine antigens no longer protect adequately against currently circulating viruses”.

They also acknowledge that boosting may already be appropriate for “recipients of vaccines with low efficacy or those who are immunocompromised”.

However, the authors warn that there could be other untoward health risks if boosters are widely introduced too soon, as this could increase the chances of side-effects – and undermine vaccine acceptance.

“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,” says Dr Soumya Swaminathan, WHO Chief Scientist and a co-author of the study.

They also 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 argue.

Aside from the WHO and FDA, other authors in the study were from the University of Washington (USA), University of Oxford (UK), University of Florida (USA), University of the West Indies (Jamaica), University of Bristol (UK), Universidad Nacional Autonoma de Mexico (Mexico), Wits Reproductive Health and HIV Institute (South Africa), Universite de Paris (France), and the INCLEN Trust International (India).

“WHO’s Strategic Advisory Group of Experts on Immunization,(SAGE), which develops WHO’s immunisation policy, is actively reviewing all the evidence including the data and this issue,” according to the Lancet press release, which notes that the paper does not constitute a formal policy position for WHO.


Image Credits: Roger Starnes / Unsplash.

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