Moderna's seasonal flu vaccine, mRNA-1010, now known as mFLUSIVA, is undergoing review by the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) on June 18, 2026. This comes after the FDA initially issued a refusal to file letter in February, citing concerns that Moderna had not used a high-dose vaccine as a comparator for older populations, which is considered standard of care. This decision shocked the biopharma world, as then-Center for Biologics Evaluation and Research (CBER) director Vinay Prasad intervened in the application.
However, days after the initial refusal, the FDA reversed its course, allowing the application to proceed with a decision date set for August. The approval request was subsequently narrowed to focus on specific age groups. Documents released ahead of the June 18 meeting indicate a softening of the FDA's stance, with Jefferies analysts noting that the regulator appears to have determined that the submitted immunogenicity data support the vaccine's efficacy in people over 65. The FDA also noted no major safety issues or imbalances in adverse events between groups, and the shot showed superior relative vaccine efficacy compared to a standard-dose comparator in patients aged 50 to 64.
Despite the positive shift, the FDA has flagged a few uncertainties for the advisory committee to review. These include evidence gaps due to data being available from only one flu season, and the lack of established efficacy in immunocompromised individuals and very frail older adults. To address these concerns, Moderna has proposed a bifurcated approach to approval: seeking traditional approval for adults aged 50 to 64 and accelerated approval for those 65 and older, with a promised confirmatory study to verify benefit in the older population. The VRBPAC will vote on whether the benefits of mFlusiva outweigh its risks for these two age groups, and the FDA aims to make an approval decision by August 5, 2026.
The initial refusal-to-file controversy stemmed from the FDA's concern about the comparator vaccine used in Moderna's Phase 3 trial, which enrolled over 40,000 adults aged 50 and older. Moderna had compared its mRNA-1010 to a licensed standard-dose influenza vaccine, despite earlier FDA feedback in April 2024 stating that while this was "acceptable," a vaccine preferentially recommended for older adults was "recommended." Moderna proceeded with the acceptable design, leading to the later rejection. The issue now appears largely resolved, and investor concerns have eased, with Moderna's stock (MRNA) rising more than 6% after the release of the briefing documents.
