Moderna's mRNA Flu Vaccine mFlusiva Wins Unanimous FDA Panel Endorsement

Moderna's mRNA Flu Vaccine mFlusiva Wins Unanimous FDA Panel Endorsement

On June 18, 2026, the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously (9-0) that the benefits of Moderna's experimental mRNA influenza vaccine, mFlusiva (mRNA-1010), outweigh its risks for adults aged 50 to 64. The panel also voted unanimously in favor of its benefit-risk profile for adults aged 65 and older. Moderna is seeking standard approval for the 50–64 cohort and accelerated approval for the 65-plus cohort, with an FDA regulatory decision expected by the PDUFA target date of August 5, 2026.

This endorsement represents a dramatic regulatory turnaround. Earlier in 2026, the FDA issued a "Refuse to File" letter, declining to review Moderna's application on the grounds that the trial was not adequately controlled. Following public backlash and a formal meeting, the FDA reversed its decision. This shift coincides with a broader transition at the FDA, marked by the departures of stricter vaccine officials (such as Vinay Prasad and former commissioner Marty Makary) and a return to what analysts describe as a "less-harsh regulatory stance."¹²

Clinical Efficacy and Evidence Gaps

The application is supported by Phase 3 clinical data published in the New England Journal of Medicine showing that mRNA-1010 reduced the likelihood of influenza illness by 27% compared to a standard-dose flu vaccine in adults aged 50 and older.

However, FDA staff reviewers flagged several evidence gaps in briefing documents:

• Single-Season Data: Efficacy data was accumulated over only one flu season (2024-2025). Due to the high severity of that season, the trial captured its target case threshold (968 cases versus the planned 836) rapidly, ending early.
• Influenza B Deficit: Because of low circulation during the trial period, there were very few confirmed influenza B cases, leaving its efficacy against B strains largely unproven.
• Subpopulation Gaps: There was a lack of robust data for frail elderly individuals, immunocompromised patients, and individuals receiving concurrent respiratory vaccines (e.g., COVID-19 or RSV).

To address these limitations, Moderna has agreed to conduct a massive post-marketing confirmatory trial involving up to 800,000 participants over two flu seasons to verify the vaccine's clinical benefits in elderly and vulnerable populations.

"The studies that were presented today were very well conducted. They have very clear results that are very robust. ... Putting it all together, the benefits outweigh the problems, the risks, in my opinion." — Flor Munoz-Rivas, Baylor College of Medicine, and Stanley Perlman, University of Iowa, VRBPAC Panelists