FDA Reverses Decision, Will Review Moderna's mRNA Flu Vaccine After Amended Application

The FDA agreed Wednesday to review Moderna's application for its experimental mRNA-based influenza vaccine after initially rejecting it last week, following a Type A meeting that produced a revised regulatory approach. The agency set a Prescription Drug User Fee Act goal date of August 5, 2026, for a decision on the application.

Moderna proposed a regulatory pathway based on age, seeking full approval for adults 50 to 64 years of age and accelerated approval for adults 65 and older, along with a post-marketing requirement to conduct an additional study in older adults. Following submission of the amended application, the FDA accepted the biologics license application for review.

The initial refusal-to-file letter, signed by the director of the FDA's Center for Biologics Evaluation and Research, stated that the application was declined because Moderna used a licensed standard-dose influenza vaccine as the comparator in its 40,000-person clinical trial. The letter argued that the study lacked an "adequate and well-controlled" comparator representing the best available standard of care. The agency took issue with the comparator vaccine used in the trial rather than one of three shots the CDC preferentially recommends for older adults as more protective against the virus.

Moderna publicly objected to the initial rejection, stating that while the FDA had recommended a different approach, the agency ultimately agreed to the study's design 18 months ago. The company said it included data from a separate trial comparing its mRNA shot to a high-dose flu vaccine when it submitted the application. The company stated that at no time in the pre-submission written feedback or meeting did the Center for Biologics Evaluation and Research indicate that it would refuse to review the file. The FDA raised no safety concerns about mRNA-1010.

The Type A meeting between Moderna and FDA officials was scheduled more quickly than is typical. Such meetings typically don't happen for 30 to 60 days after a refuse to file letter is received.

An agency spokesperson said Wednesday that discussions with the company led to a revised regulatory approach and an amended application, which FDA accepted. The agency stated it will maintain its high standards during review and potential licensure stages as it does with all products.

Pending review and FDA approval, mRNA-1010 would be available for U.S. adults 50 years of age and older, including adults 65 and older, for the 2026-2027 flu season. The company's total investment in the shot is over a billion dollars, including up to $750 million from Blackstone, an asset management firm.

The clinical trial concluded Moderna's new vaccine was more effective in adults age 50 and older than one of the standard flu shots used today. Results published in the New England Journal of Medicine found that Moderna's mRNA flu vaccine was more than 20% more effective than a traditionally produced influenza vaccine in adults.

mRNA-1010 has now been accepted for review in the United States, Europe, Canada and Australia with further submissions planned in 2026. Moderna expects the first potential approvals for mRNA-1010 in 2026, subject to various ongoing regulatory reviews.

Shares of Moderna rose more than 5% after the announcement in morning trading, with shares up more than 8% at certain points Wednesday morning.

The highly unusual public dispute was the latest sign of the FDA's heightened scrutiny of vaccines under the current Health Secretary, particularly those using mRNA technology. In the past year, FDA officials have rolled back recommendations around COVID-19 shots, added extra warnings to the two leading COVID vaccines, and removed critics of the administration's approach from an FDA advisory panel. The Trump administration last summer canceled almost $500 million in contracts for the development of mRNA vaccines to prevent viral threats and biological attacks. The federal Biomedical Advanced Research and Development Authority canceled 22 contracts with researchers and universities for the study of mRNA technology.

Reeling from lowered sales of its COVID-19 vaccine, Moderna has been heavily scrutinized for its use of messenger RNA technology. As a result of the challenging climate, Moderna said it would no longer invest in late-stage trials for vaccines and is shifting its focus to oncology.