Giving a booster dose to the entire population is not “appropriate” at this time of the pandemic due to the high efficacy of current vaccines in preventing severe COVID-19, including the delta variant, according to a published international study this monday in the magazine “The Lancet”.
The research, conducted by an international team involving scientists from the World Health Organization (WHO) and other institutions, has examined data from all published clinical trials and observational studies.
Based on their analysis, the experts confirm that existing vaccines “continue to be highly effective against severe disease”, even that produced by the most risky variants.
According to an average of the results obtained in observational studies, current vaccination shows an efficacy of 95% against severe disease, both for the delta and for the alpha variant, and 80% against infection by either of them.
Scientists point out that in all types of vaccines and variants, protection is higher against severe disease than against mild.
The authors add that, although vaccines are known to be somewhat less effective against asymptomatic COVID-19 and transmission, in populations with a high rate of inoculations, the minority of unvaccinated is the main vector of infections, as well as the group most at risk of severe COVID-19.
Experts emphasize that, even if the antibodies against the virus in vaccinated people drop over time, that “does not necessarily mean a reduction in the effectiveness of vaccines against severe disease.”
This could be, they add, because protection against virulent COVID-19 “is mediated not only by antibody responses, which may be short-term in some vaccines, but also by memorized (immune) responses and cell-based immunity. , which generally last longer. ”
“Taken together, the available studies do not provide credible evidence that there is a substantial decline in protection against severe disease, which is the main goal of vaccination,” says one of the authors of the study published in “The Lancet. “, Ana María Henao-Restrepo.
This specialist argues that, since the supply of vaccines is limited, the greatest number of lives can be saved if the preparations “are offered to people who have an appreciable risk of becoming seriously ill and have not yet been vaccinated.”
Even if there were ultimately some benefit to giving the booster shot, it would not outweigh the benefits of providing that initial protection to people who have not yet been inoculated, he says.
Henao-Restrepo points out that if vaccines are administered where they are most needed, this “could accelerate the end of the pandemic by inhibiting the evolution of the variants.”
Experts say that if booster vaccines are eventually used, the specific circumstances and population groups in which the benefits outweigh the risks will have to be identified.
They also maintain that, in any case, a booster dose will be more useful and lasting if a preparation designed to combat future new variants, and not the current ones, is administered.
Study co-author Soumya Swaminathan cautions that, “although the idea of reducing the number of COVID-19 cases by increasing immunity in already vaccinated people is attractive,” any decision in this regard “must be based on” scientific and “weigh the risks to people and society.”