New York, Sep 14 (IANS): Vaccine efficacy against severe Covid-19 is so high, even for the Delta variant, that booster doses for the general population are "not appropriate" at this stage in the pandemic, an international group of scientists argued in a review published in The Lancet.

The review, which includes scientists from the World Health Organization (WHO) and two from the US Food and Drug Administration (FDA), who will leave the agency, comes even as the latter is currently reviewing evidence for booster doses for Americans; and many other countries including Israel, Italy, France and Russia who have already rolled out the third dose of Covid jabs.

It summarises the currently available evidence from randomised controlled trials and observational studies published in peer-reviewed journals and pre-print servers and asserts that the benefits of the first shots are clear.

It added that vaccination had 95 per cent efficacy against severe disease both from the Delta variant and from the Alpha variant, and over 80 per cent efficacy at protecting against any infection from these variants.

Although vaccines are less effective against asymptomatic disease or against transmission than against severe disease, the unvaccinated minority are still the major drivers of transmission, the scientists argued in the review published on Monday.

"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. Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated," said lead author Ana-Maria Henao-Restrepo from the WHO.

Last week, Pascal Soriot, CEO of AstraZeneca, also said that a third dose of vaccines against Covid-19 may not be needed for everyone.

Writing in the Telegraph, he stated that the decision to jab the entire population must be based on "real world clinical effectiveness data, not simply antibody measurements".

The WHO has, meanwhile, called for an extension of a global moratorium on Covid-19 booster doses, with an aim to enable every country to vaccinate at least 40 per cent of its population.

According to the WHO, globally 5.5 billion vaccine doses have been administered, but 80 per cent have been administered in high- and upper-middle income countries.

WHO Director-General Tedros Adhanom Ghebreyesus reiterated that third doses may be necessary for the most at-risk populations, but for now, "we do not want to see widespread use of boosters for healthy people who are fully vaccinated".

"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," adds co-author Soumya Swaminathan, WHO Chief Scientist.