Study of Covid Booster Shot Benefits Fans Debate Over Extra Doses

Wading into an acrimonious debate over booster doses, researchers in Israel reported on Wednesday that a third dose of the Pfizer-BioNTech coronavirus vaccine can prevent both infections and severe illness in adults older than 60 shortly after the injection.

The study, published in the New England Journal of Medicine, is the latest salvo in the conflict over whether booster doses are needed for healthy adults and whether they should be given out, as the Biden administration plans to do, when so much of the world remains unvaccinated.

Several independent scientists said the cumulative data so far suggest that only older adults will need boosters — and maybe not even them.

Vaccination remains powerfully protective against severe illness and hospitalization in the vast majority of people in all of the studies published so far, experts said. But the vaccines do seem less potent against infections in people of all ages, particularly those exposed to the highly contagious Delta variant.

What the Israeli data show is that a booster can enhance protection for a few weeks in older adults — a result that is unsurprising, experts said, and does not indicate long-term benefit.

“What I would predict will happen is that the immune response to that booster will go up, and then it will contract again,” said Marion Pepper, an immunologist at the University of Washington in Seattle. “But is that three- to four-month window what we’re trying to accomplish?”

Federal health officials — including Dr. Anthony S. Fauci, President Biden’s top medical adviser on the pandemic — have justified plans to distribute booster shots by pointing to emerging evidence from Israel and other countries suggesting that immunity from vaccination wanes over time.

The idea has sent some Americans scrambling for booster shots even before they are formally authorized, a step the F.D.A. may take as soon as Friday. But even among government scientists, the idea has been met with skepticism and anger.

Two scientists who lead the F.D.A.’s vaccine branch said they would leave the agency this fall, in part because of their unhappiness over the administration’s push for booster doses before federal researchers could review the evidence.

On Monday, an international group of scientists, which included the departing F.D.A. officials, decried the push for boosters. In their review, published in The Lancet, the scientists analyzed dozens of studies and concluded that the world would be better served by using vaccine doses to protect the billions of people around the world who remain unvaccinated.

“Our primary goal here in this pandemic was, first of all, to avoid, to end all preventable deaths,” said Dr. Soumya Swaminathan, chief scientist at the World Health Organization and a co-author of The Lancet review. “And since we have the tools to do that very effectively, we should be using it to prevent deaths around the world.”

To prevent the virus from morphing into even more dangerous forms than the Delta variant — and perhaps into one that evades the immune response entirely — the more urgent need, experts said, is to protect the unvaccinated, both in the United States…