In this Sept. 14, 2021 file photo, a syringe is prepared with the Pfizer COVID-19 vaccine at a clinic at the Reading Area Community College in Reading, Pa. Credit: Matt Rourke / AP

The COVID-19 vaccine booster shot proposed by Pfizer Inc. and BioNTech SE should be given to older Americans and those at high risk, a panel of expert advisers to the U.S. Food and Drug Administration said Friday, rejecting a request for broader distribution.

While the recommendation isn’t binding, it’s a blow to the Biden administration’s plan to deliver third doses to all American adults in the coming weeks to stave off the virus’s spread. The FDA will have to decide in the coming days whether to follow suit or overrule its trusted scientific advisers and proceed with a broader booster authorization.

Pfizer had originally proposed approving a booster shot for everyone 16 and older. But the advisers rejected that idea out of concern that the data to support such a broad application was thin and there could be risks, especially for younger people.

“It’s not clear to me that the data we’re seeing right now is applicable or necessary for the general population,” said National Institutes of Health scientist Michael Kurilla. Another panelist, Paul Offit of the Children’s Hospital of Philadelphia, said he wanted to see more data on the risk of heart inflammation in younger men.

Instead, the panel voted 18-0 in favor of an emergency-use authorization — a more limited clearance than a full approval — for people 65 and older or individuals at high risk of severe COVID-19. The vote didn’t specify what was meant by “high risk,” though panelists later agreed the authorization could include people who may be exposed to COVID-19 because of their jobs, such as health care workers.

The move is a setback to a sweeping plan from the Biden administration to roll out booster shots to a broad population next week. In August, the president had said everyone who had been vaccinated would be able to receive a third dose at least eight months after their most recent dose.

Still, the administration called it “an important step” toward its fight against the pandemic. “We stand ready to provide booster shots to eligible Americans once the process concludes at the end of next week,” White House spokesman Kevin Munoz said.

Peter Marks, head of the FDA’s vaccine program, made clear to panelists Friday that the agency would make its own decision.

“We are not bound at FDA by your vote, just so you understand that,” he said. “We can tweak this as need be.”

Pfizer said it will “work with the FDA following today’s meeting to address the committee’s questions, as we continue to believe in the benefits of a booster dose for a broader population.”

If the FDA follows the advisers’ recommendation, U.S. health officials would still be able to target third doses at people at highest risk of getting seriously ill or dying from COVID-19 — at least those who took Pfizer’s vaccine. Moderna has also applied to the FDA for emergency authorization of a third dose booster, while the agency is still waiting for data backing an additional dose from Johnson & Johnson.

The FDA may make its decision on Pfizer in the coming days. An outside advisory panel to the Centers for Disease Control and Prevention will also make detailed recommendations for the use of the booster shot at a meeting next week.

Shares of Pfizer declined 1.3 percent at the close of trading in New York, and BioNTech shares were down 3.6 percent. Shares of Moderna Inc., maker of a similar COVID vaccine, were down 2.4 percent.

Arnold Monto, acting chair of the advisory committee, also left the door open for the group to recommend emergency use authorization for boosters in younger people later, when more information becomes available about potential side effects and effectiveness.

“That’s the beauty of an EUA,” he said. “It can be changed based on changing data.”

Story by Robert Langreth and Fiona Rutherford.