Vaccines effective even against coronavirus variants, no booster needed yet, say scientists

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New Delhi: The efficacy of vaccines in preventing severe COVID-19 – even for the delta version – is so high that an additional or booster dose for the general population is not appropriate at this stage in the pandemic, a new study has said. paper published on monday the Lancet.

Some researchers from the World Health Organization (WHO) and the US Food and Drug Administration (FDA), after summarizing currently available evidence from clinical trials and observational studies published in peer-reviewed journals and pre-print servers come to the conclusion. .

The researchers said observational studies show that vaccines remain highly effective against severe disease, even when infections are caused by different types.

“The vaccines currently available are safe, effective and life-saving. While the idea of ​​further reducing the number of COVID-19 cases by boosting immunity in vaccinated people is tempting, any decision to do so must be evidence-based and consider the benefits and risks to individuals and society. Soumya Swaminathan, WHO chief scientist and co-author of the paper, said in a statement.

“These high-stakes decisions should be based on strong evidence and international scientific discussion,” she said.

On average, such studies show that vaccination against severe disease from both delta and alpha types had 95 percent efficacy, and more than 80 percent efficacy in protecting against any infection from these types.

Although vaccines are less effective against asymptomatic disease or against transmission, even in populations with high vaccination coverage, it is the disproportionate minority that induces transmission, the researchers said.

“Taken as a whole, the currently available studies do not provide reliable evidence of a reduction in protection against serious disease, which is the primary goal of vaccination,” said lead author Ana-Maria Henao-Restrepo, Research and Development Unit, WHO chief, said in a statement.

“The limited supply of these vaccines would most likely save lives if made available to people who are at appreciable risk of serious disease and have not yet received a vaccine. Even if some benefit could eventually be gained from boosting, it would not outweigh the benefits of providing early protection without vaccination,” she adds.

“If vaccines are deployed where they will do best, they could hasten the end of the pandemic by preventing further development,” the paper also reported.

Read also: How Covid eased India’s influenza problem and why experts say it’s not good news yet

Condition for using Booster

The researchers note that even though antibody levels decrease over time in vaccinated individuals, this does not necessarily predict a decrease in the efficacy of vaccines against serious disease.

Protection against severe disease is mediated not only by antibody responses but also by memory responses and cell-mediated immunity – facilitated by white blood cells known as T cells and B cells, which normally live longer. Lives.

If the booster is to be used eventually, specific situations will need to be identified where the benefits outweigh the risks, the researchers conclude.

The team also notes that if there are new types that can evade the current vaccine-induced immune response, they are most likely to do so from strains that have already become widely prevalent.

It would be more effective to develop booster vaccines to counter potential new variants than to give boosters that use existing vaccines.

This would be similar to the strategy used for influenza vaccines, for which each annual vaccine is based on the most current data about circulating strains, increasing the likelihood that the vaccine will remain effective even if further strain development occurs. .

(Edited by Paramita Ghosh)

Read also: How covid is on its way to become just another virus

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