For most Americans, the coronavirus has become a tolerable threat, on par with the flu, and requires minimal precautions, if any. But for older people and the immunocompromised, the virus still poses a formidable risk.

Roughly 300 people in the United States are still dying from COVID-related causes each day, a vast majority of them adults older than 70 and people who are medically frail or have impaired immune systems. So should older people and the medically vulnerable get another booster shot now?

That’s the thorny question facing federal health officials.

About 53 million adults 65 and older live in the United States, accounting for about 16% of the population, according to the Census Bureau. And 7 million Americans have weak immune systems because of an illness or a medication.

Although infection with the coronavirus can be a matter of inconvenience or a mild illness for a relatively young and healthy adult, COVID can spell severe disease, hospitalization and death for older adults and immunocompromised people, said Dr. Celine Gounder, an infectious disease physician and senior fellow at the Kaiser Family Foundation.

“I think it’s reasonable to boost immunocompromised people and people in nursing homes every six months,” Gounder said. “I do not think that annual boosters for everyone makes sense.”

Some Americans who got their latest boosters in the fall are asking their doctors when they should get the next dose. Britain and Canada have already recommended additional shots for older adults and immunocompromised people starting this spring.

It’s unclear whether the Food and Drug Administration will follow suit. In a bid to simplify what had become a bewildering array of guidelines on vaccination, the agency said in January that it would move to a single shot offered each fall to all Americans, as is the case for flu.

“We hope that simplifying the COVID-19 vaccine regimen in the not-too-distant future will lead to the vaccination of more individuals in the coming years,” the agency said in a statement.

A one-size-fits-all approach may not work. Americans are “diverse in our age, we’re diverse in our risk, we’re diverse in our perceptions of risk,” said Dr. Ofer Levy, director of the precision vaccines program at Boston Children’s Hospital and an adviser to the FDA.

Ideally, Levy said, a high-risk person would be able to consult with a health care provider and decide whether an additional dose of the vaccine was needed.

Immunity against infection declines after just a few months in nearly everyone who is vaccinated. But in people with weak immune systems, protection from a booster shot in the fall “wanes fast enough that by the spring or summer they are no longer distinguishable from people who didn’t get boosted,” said Dr. Jeremy Faust, an emergency medicine physician and health policy expert at Brigham and Women’s Hospital in Boston.

“Immunocompromised people have a very, very short period of benefit from the booster,” Faust said. “And so you have to re-up it.”

Faust cited data on the first round of boosters, which were offered in the fall of 2021 and which targeted the original version of the virus. There is much less research on the effectiveness of the bivalent boosters that were released last fall, and there is no data on the ideal timing for the next round of additional vaccines.

The dearth of information leaves some experts hesitant to recommend another shot for any group of people, even the most vulnerable.

“Given the lack of data, I don’t think it’s fair to say to people, ‘Inject yourself with a biological agent,’” said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and an adviser to the FDA.

“It’s incumbent upon them when they make recommendations to show the data on which that recommendation is based,” Offit said of federal health officials. “Otherwise, they’re just saying, ‘Trust us.’”

The FDA did not comment on plans to consider offering boosters more frequently than once a year.

“We continue to closely monitor the emerging data in the United States and globally, and we will base any decision on additional updated boosters upon those data,” the agency said in a statement.

Even if the FDA were to authorize another booster shot this spring, it’s unclear how many people would choose to get it. Just over 16% of Americans, and only 42% of adults older than 65, have opted for the bivalent shots.

“If boosters work, they’ll only work if people get them,” said Dr. Eric Rubin, editor-in-chief of The New England Journal of Medicine and an adviser to the FDA. “That’s a much larger issue than an additional booster.”

Dr. Camille Kotton, who treats immunocompromised patients at Massachusetts General Hospital in Boston, said a majority of them were not up to date with their vaccines. She cited many possible reasons: They are not aware of the recommendations, they find the information too confusing or they are simply ready to move on from the pandemic.

“It’s nice to focus on another dose of bivalent vaccine, but I do worry that we haven’t even given the bivalent vaccine to the majority of immunocompromised and elderly,” she said. “Maybe we should focus on those populations.”

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This article originally appeared in The New York Times.