Annual COVID-19 shots for healthy younger adults and children will no longer be routinely approved under a major new policy shift unveiled Tuesday by the Trump administration.

Top officials for the Food and Drug Administration laid out new requirements for yearly updates to COVID shots, saying they'd continue to use a streamlined approach that would make vaccines available to adults 65 and older as well as children and younger adults with at least one health problem that puts them at higher risk.

But the FDA framework urges companies conduct large, lengthy studies before tweaked vaccines can be approved for healthier people. In a framework published Tuesday in the New England Journal of Medicine, agency officials said the approach still could keep annual vaccinations available for between 100 million and 200 million adults.

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The upcoming changes raise questions about people who may still want a fall COVID-19 shot but don't clearly fall into one of the categories.

“Is the pharmacist going to determine if you're in a high-risk group?” asked Dr. Paul Offit, a vaccine expert at Children's Hospital of Philadelphia. “The only thing that can come of this will make vaccines less insurable and less available.”

The framework, published in the New England Journal of Medicine, is the culmination of a series of recent steps scrutinizing the use of COVID shots and raising major questions about the broader availability of vaccines under President Donald Trump.

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For years, federal health officials have told most Americans to expect annual updates to COVID-19 vaccines, similar to the annual flu shot. Just like with flu vaccines, until now the FDA has approved updated COVID shots when manufacturers provide evidence that they spark just as much immune protection as the previous year's version.

But FDA's new guidance appears to be the end of that approach under Health Secretary Robert F. Kennedy, who has filled the FDA and other health agencies with outspoken critics of the government’s handling of COVID shots, particularly their recommendation for young, healthy adults and children.

Tuesday’s update, written by FDA Commissioner Marty Makary and FDA vaccine chief Vinay Prasad, criticized the U.S.’s “one-size-fits-all” approach and states that the U.S. has been “the most aggressive” in recommending COVID boosters, when compared with European countries.

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“We simply don’t know whether a healthy 52-year-old woman with a normal BMI who has had Covid-19 three times and has received six previous doses of a Covid-19 vaccine will benefit from the seventh dose,” they wrote.

Outside experts say there are legitimate questions about how much everyone still benefits from yearly COVID vaccination or whether they should be recommended for people at increased risk. An influential panel of advisers to the Centers for Disease Control and Prevention is set to debate that question next month.

The FDA framework announced Tuesday appears to usurp that advisory panel's job, Offit said. He added that CDC studies have made clear that booster doses do offer protection against mild to moderate illness for four to six months after the shot even in healthy people.