U.S. health regulators are defending their handling of Moderna’s mRNA flu vaccine application after initially declining to review it, while signaling the decision may not be final.
Moderna said this week that the Food and Drug Administration rejected its request to submit a formal approval application, according to The New York Times.
That was despite late-stage trials involving about 41,000 participants that found the vaccine to be safe and effective for adults 50 and older.
The decision was made by Dr. Vinay Prasad, the agency’s top vaccine regulator, who overrode staff recommendations.
FDA Commissioner Dr. Marty Makary said in a television interview that the agency’s response was part of routine discussions with drug makers and that regulators would continue working with the company, raising the possibility of future approval.
The Department of Health and Human Services said regulators had asked Moderna to use a high-dose flu vaccine as a comparison in adults 65 and older during a large study.
Andrew Nixon, an HHS spokesman, said Moderna used a standard flu shot made by drugmaker GlaxoSmithKline, known as GSK, as the comparison vaccine in the study instead of a higher-dose option often given to seniors, and he argued that choice could have left some older participants less protected.
Moderna rejected that criticism, saying FDA staff agreed in meetings starting in April 2024 that the GSK flu shot was an acceptable vaccine to use for comparison in the trial.
Company spokesman Chris Ridley said the FDA’s communications indicated Moderna could proceed under that design.
According to a person familiar with the matter, the rejection created internal disagreement within the agency, including differences between Dr. Prasad and Dr. David Kaslow, director of the Office of Vaccines Research and Review.
Makary also cited concerns raised by some about whether the chosen control vaccine was appropriate for seniors.
A senior FDA official said Health Secretary Robert F. Kennedy Jr. was not involved in the review.
Moderna said Blackstone invested $750 million in the experimental vaccine, which the company says could be produced more quickly in response to emerging flu strains and tailored more easily to specific countries.
The agency’s refusal to review the application is uncommon.
The dispute follows other recent federal funding reductions affecting mRNA vaccine projects, including the cancellation of a contract related to bird flu vaccine development.
Jim Mishler ✉
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