The FDA and other public health agencies around the world continue to examine evidence on Covid-19 vaccine efficacy and the role booster doses of vaccine might play in improving immunity against the disease.
For the new paper in The Lancet, the scientists note that they reviewed randomized trials and observational studies on Covid-19 vaccines and consistently find that “vaccine efficacy is substantially greater against severe disease than against any infection; in addition, vaccination appears to be substantially protective against severe disease from all the main viral variants. Although the efficacy of most vaccines against symptomatic disease is somewhat less for the delta variant than for the alpha variant, there is still high vaccine efficacy against both symptomatic and severe disease due to the delta variant.”
The scientists note that there is an opportunity right now to study variant-based boosters before there could be a widespread need for them. But they also argue in their paper that the current Covid-19 vaccine supply could “save more lives” if used in people who are not yet vaccinated than if used as boosters. In early August, the World Health Organization called for a moratorium on booster shots until at least the end of September.
“To date, none of these studies has provided credible evidence of substantially declining protection against severe disease, even when there appear to be declines over time in vaccine efficacy against symptomatic disease,” the scientists write in their paper.
“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. Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated,” the scientists write. “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.”
The paper published just shy of a month after US federal health officials announced plans for booster doses of Covid-19 vaccine to be offered this fall, starting September 20, subject to authorization from the FDA and sign off from the US Centers for Disease Control and Prevention.
The FDA’s Vaccines and Related Biological Products Advisory Committee is meeting this Friday to discuss vaccine makers Pfizer and BioNTech’s application to administer their Covid-19 vaccine as a third dose, or “booster” shot, to people ages 16 and older.
CNN has reached out to the FDA for comment on the Lancet review.