In Review, Top F.D.A. Scientists Question Imminent Need for Booster Shots

Federal health officials have said that one reason they announced the booster plan was to stay ahead of the virus and be ready for when vaccines may no longer protect as well against severe cases of Covid-19. Those officials, including Dr. Anthony S. Fauci, Mr. Biden’s chief medical adviser, have relied heavily on data presented to them by Israeli officials, who have defended that country’s early, aggressive booster campaign.

Their data, Dr. Fauci and other administration officials have said, show a clear waning of immunity against infection, with enhanced protection from booster doses, but show only hints of waning immunity against hospitalization in people under 65.

But in the new review, Dr. Krause, Dr. Gruber and other vaccine experts said that more time and public discussion, and better studies, were needed to determine if boosters were needed for the general population. They also said that whatever advantage the shots might provide would not outweigh the benefit of using them to protect the billions of people who remain unvaccinated worldwide.

The World Health Organization has asked wealthy countries to hold off on administering extra shots to healthy patients until at least the end of the year as a way of enabling every country to vaccinate at least 40 percent of its population. Every unvaccinated person provides an opportunity for the virus to morph into new, potentially dangerous, variants, scientists have warned.

The review authors did, however, say that extra shots might be useful for some people with weak immune systems — a step the F.D.A. already authorized.

“As more information becomes available, it may first provide evidence that boosting is needed in some subpopulations,” they wrote. “However, these high-stakes decisions should be based on peer-reviewed and publicly available data and robust international scientific discussion.”

They were largely dismissive of the Israeli data and other studies that some health officials have said make the case for imminent extra shots. They said some Israeli evidence was collected just a week or so after the third dose and might not hold up over time, and that “a very short-term protective effect would not necessarily imply worthwhile long-term benefit.”