By Liz Essley Whyte

The Trump administration released a more stringent set of guidelines for approving Covid-19 vaccines, requiring more evidence for new shots for healthy adults and children.

Any new Covid vaccines for many children and adults will be required to undergo randomized, controlled trials before receiving Food and Drug Administration approval, FDA Commissioner Dr. Marty Makary and the agency's new vaccines chief, Dr. Vinay Prasad, wrote Tuesday in the New England Journal of Medicine. The agency expects it will be able to approve the shots for adults older than 64 and high-risk groups based on antibody testing but will encourage drugmakers to conduct more randomized trials for those shots too.

The original Covid-19 shots were tested in large, randomized controlled trials against placebos. Subsequent versions, updated to match new strains, were tested to ensure they triggered immune systems to fight the virus. Such testing looks for antibodies in people who have received the shots and is easier to conduct than trials looking at whether the shots prevent hospitalization or other outcomes.

"The benefit of repeat dosing -- particularly among low-risk persons who may have previously received multiple doses of Covid-19 vaccines, had multiple Covid-19 infections, or both -- is uncertain," the two men wrote. "The American people, along with many health care providers, remain unconvinced."

The leaders cited the low uptake for Covid-19 vaccines and said more evidence would help build trust in the shots. About 23% of American adults received the most recent Covid-19 shot, according to the Centers for Disease Control and Prevention.

In past years, Covid-19 vaccines have been updated each year to match the strain mostly likely to circulate in the fall and winter. Large, randomized clinical trials might be too difficult to conduct in time to update the shots for the fall. The new trial requirements could chill vaccine development, industry experts said. It is unclear whether Covid-19 vaccine manufacturers would be willing to invest in expensive, new trials for future products.

Moderna and Pfizer declined to comment.

Prasad is expected to give more details on the new framework Tuesday afternoon. A critic of some pandemic-era public health measures, he succeeded Dr. Peter Marks, who was forced out of the agency in March.

The FDA recently approved Novavax's Covid-19 vaccine for older adults and high-risk groups but required the Maryland-based company to conduct an additional clinical trial after approval.

Write to Liz Essley Whyte at liz.whyte@wsj.com

(END) Dow Jones Newswires

May 20, 2025 11:23 ET (15:23 GMT)

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