FDA Reverses Course, Agrees to Review Moderna's mRNA Flu Shot Application

FDA to Review Moderna's Novel mRNA Flu Vaccine After Dispute Resolution

The U.S. Food and Drug Administration (FDA) has reversed its earlier stance and will now review Moderna's application for its messenger RNA (mRNA)-based seasonal flu vaccine, designated mRNA-1010. This decision follows the resolution of a public dispute between the regulatory agency and the biotechnology company regarding the design of the vaccine's pivotal clinical trials. Moderna announced the change on Wednesday, February 18, 2026, approximately one week after the FDA had initially declined to review the application.

Details of the Initial Refusal and Subsequent Resolution

The dispute originated when the FDA issued a 'refusal to file' letter, a rare move that temporarily blocked the review of Moderna's application. Dr. Vinay Prasad, the FDA's vaccine director, cited concerns that Moderna's 40,000-person clinical trial, which found the vaccine more effective in adults aged 50 and older than a standard flu shot, did not include a comparison against a higher-dose flu vaccine specifically recommended for individuals 65 and older. Moderna publicly objected to this refusal, stating that while the FDA had recommended a higher-dose comparison, the agency had ultimately agreed to the study's design. The company also highlighted that it had provided additional comparison data from a separate trial that utilized a high-dose shot for older individuals.

Following a 'Type A' meeting between Moderna and the FDA's Center for Biologics Evaluation and Research (CBER), a compromise was reached. Moderna has since revised its application, seeking full approval for the vaccine's use in adults aged 50 to 64 and accelerated approval for those aged 65 and older. As part of this agreement, Moderna has committed to conducting an additional post-marketing study once the vaccine is on the market for older adults.

The Promise of mRNA Flu Vaccines

Moderna's mRNA-1010 has demonstrated promising results in its Phase 3 trials. The vaccine showed a 26.6% higher relative vaccine efficacy (rVE) compared to a licensed standard-dose seasonal influenza vaccine in adults aged 50 and older. For participants aged 65 and older, the rVE was 27.4%. The efficacy was also strong against specific influenza strains, including A/H1N1, A/H3N2, and B/Victoria lineages.

The mRNA technology offers several potential advantages over traditional flu vaccine production methods. These include a shorter production time, which could allow for a better match to circulating flu strains each season and enable a more rapid response in the event of a future influenza pandemic. The safety and tolerability profile of mRNA-1010 has been consistent with previous studies, with most adverse events being mild, such as injection site pain, fatigue, headache, and myalgia.

Next Steps and Global Reach

The FDA is targeting a decision on Moderna's application by August 5, 2026. If approved, Moderna aims to make the vaccine available for the 2026-2027 flu season for adults aged 50 and up. In addition to the United States, Moderna has also submitted applications for approval of its mRNA flu vaccine in Europe, Canada, and Australia.