The push to roll out Covid-19 booster shots is not being driven by sound scientific evidence, according to a group of international researchers writing in the theLancet medical journal Monday, who said available evidence shows vaccines to be highly effective against the delta coronavirus variant and that unwarranted messaging about booster doses undermines overall confidence in vaccines.
- Though vaccines are somewhat less effective at preventing symptomatic disease caused by the delta coronavirus variant, studies consistently demonstrate strong protection against severe and symptomatic illness, the researchers said.
- With this in mind, the available evidence does not support boosters for the general population, the researchers said, adding that touted indicators of waning immunity (such as falling antibody levels) do not necessarily point to the vaccine becoming less effective over time.
- The researchers, who included experts from the Food and Drug Administration and World Health Organization, warned that unnecessary calls for booster shots have “implications for vaccine acceptance that go beyond Covid-19 vaccines,” undermining vaccine confidence and public health messaging on the value of getting vaccinated, particularly if boosters are only used for one type of vaccine.
- There is also the potential for “significant adverse reactions” if boosters are administered too soon or used too frequently—the researchers noted the small risk of myocarditis, which is more common after the second dose of an mRNA vaccine—the researchers said, which could further undermine confidence in vaccines.
- As well as not being backed up by available scientific evidence, the researchers said the limited supply of vaccines would be able to save more lives if used in people who had not received a vaccine yet, noting that “even if some gain can ultimately be gained from boosting, it will not outweigh the benefits” of protecting the unvaccinated.
While some highly vaccinated regions, including the U.S., are battling severe Covid-19 outbreaks, the researchers emphasize the fact that “the unvaccinated are still the major drivers of transmission and themselves at the highest risk of serious disease.” Though the growing proportion of breakthrough cases may be rising, they note this would be expected even if there was no drop in vaccine efficacy due to the changing behaviors of the fully vaccinated and the greater proportion of the population made up by vaccinated people.
“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 the paper’s lead author and WHO researcher Dr. Ana-Maria Henao-Restrepo. Henao-Restrepo said the limited stock of vaccines will “save the most lives” if made available to people who have not yet received any vaccine at all.
Wealthy countries rapidly cornered the global vaccine market, ordering up supplies sometimes many times what would be needed for their population and vaccinating low risk groups while poorer countries struggled to vaccinate even the most vulnerable. The decision for many countries to roll out booster shots in the midst of this vast inequity has outraged public health leaders, and the WHO has called for a moratorium on all boosters (barring in vulnerable groups who may not have developed immunity from the first set of vaccines) until 2022 so that people might receive their first doses. The global vaccine-sharing initiative Covax, jointly led by WHO, Gavi and the Coalition for Epidemic Preparedness Innovations, was supposed to lead the way in ensuring poorer nations had access to vaccines. It is now hundreds of millions of vaccines short of its goal and has struggled to achieve this amid funding issues, difficulties accessing vaccines and the reluctance of wealthy countries to share supplies.
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The U.S. is slated to begin its booster campaign in late September, though is still awaiting approval from regulators. Though the researchers said evidence doesn’t support boosting now, they acknowledged they may be needed at some point in the future, such as if a new vaccine-evading variant emerges or immunity is shown to fade over time.