Research on Covid Booster Shots is Conflicting

New research indicated the booster shots were not now necessary for everyone, a view that prevailed at the agency’s advisory committee meeting.,

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The F.D.A.’s day of lively debate revealed key questions about the evidence on boosters.

Mark Turney, 66, a kidney transplant patient, received a booster shot of the Pfizer-BioNTech Covid-19 vaccine in Hartford, Conn., last month. Scientists are debating the need for a third shot.
Mark Turney, 66, a kidney transplant patient, received a booster shot of the Pfizer-BioNTech Covid-19 vaccine in Hartford, Conn., last month. Scientists are debating the need for a third shot.Credit…Joseph Prezioso/Agence France-Presse — Getty Images
  • Sept. 17, 2021Updated 6:45 p.m. ET

Advisers to the Food and Drug Administration on Friday questioned a key assertion by researchers in Israel and by the drug company Pfizer: that its coronavirus vaccine is waning in protection not just against infection, but against severe illness and hospitalization.

The advisers met to evaluate Pfizer’s application for approval of booster vaccine doses for all Americans over age 16. Among the details that surfaced during the lively debate: Israel and the United States define severe illness differently.

In Israel, anyone with an accelerated respiratory rate and an oxygen level of below 94 percent is severely ill. By contrast, the Centers for Disease Control and Prevention considers people who are sick enough to be hospitalized as having severe disease, Dr. Sara Oliver, a C.D.C. scientist, said at the advisory committee meeting.

The discrepancy might help explain why the two countries have reported vastly different outcomes in people who are fully immunized.

Israeli researchers said they have seen large numbers of hospitalized patients who had received two doses months earlier. But in the United States, the C.D.C. has reported that vaccinated patients make up just 2 percent of people hospitalized for Covid-19.

It is just one of many scientific discrepancies that came to light this week.

On Monday, in the journal The Lancet, an international team of scientists analyzed dozens of studies and concluded that boosters are not yet needed by the general population, and that the world would be better served by using vaccine doses to protect the billions of people who remain unvaccinated.

On Wednesday, scientists at the F.D.A. posted an assessment online hinting that they, too, are unconvinced that there’s enough evidence that boosters are needed.

“Overall, data indicate that currently U.S.-licensed or authorized Covid-19 vaccines still afford protection against severe Covid-19 disease and death in the United States,” according to their executive summary.

But some F.D.A. leaders have publicly endorsed booster shots. “The need for an additional dose at six months to provide longer-term protection should not come as a surprise, as it’s likely necessary for the generation of a mature for immune response,” Dr. Peter Marks, one of the agency’s top officials, said in the meeting on Friday.

Alarmed by the rise in cases, Israeli officials have offered third doses of the vaccine to everyone older than 12. Researchers from Israel published early results from that rollout on Wednesday in the New England Journal of Medicine — but few outside scientists found the study convincing.

The team collected data on the effects of booster shots from the health records of more than 1.1 million people over age 60. At least 12 days after the booster, rates of infection were elevenfold lower — and rates of severe disease nearly twentyfold lower — in those who received a booster compared with those who had received only two doses, the researchers found.

The results are unsurprising, experts said, and do not indicate long-term benefit.

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Dr. Celine Gounder, an infectious disease expert at Bellevue Hospital in New York and a former member of the Biden-Harris Covid-19 advisory council.Credit…Amr Alfiky/The New York Times

“We have known for some time that the vaccines elicit less robust immune responses in the elderly,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center and a former adviser to the Biden administration. “Recommending additional doses of vaccine for the elderly isn’t controversial.”

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.

The cumulative data so far suggest that only older adults will need boosters, a view underscored by the F.D.A.’s advisory committee, which voted on Friday to endorse boosters only for Americans aged 65 and older, and those who are at risk for severe illness.

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