FDA advisory panel backs Moderna's mRNA seasonal influenza vaccine for adults 50 and older

A federal advisory panel recommended — by a 9–0 vote — that the benefits of Moderna’s mRNA‑1010 seasonal influenza vaccine outweigh its risks for adults 50 through 64 and for adults 65 and older.

The Vaccines and Related Biological Products Advisory Committee met June 18 to review clinical, immunogenicity and safety data for mRNA‑1010, Moderna’s candidate seasonal influenza vaccine. Moderna presented results from the pivotal, event‑driven Phase III trial (P304), which enrolled roughly 40,800 adults. The sponsor reported a relative vaccine efficacy (RVE) of 26.6% for mRNA‑1010 compared with U.S. standard‑dose influenza vaccine (Moderna speaker: "It demonstrated increased vaccine efficacy of 26.6% over the comparator vaccine"), and higher HAI titers and CD4 T‑cell responses across strains in immunogenicity assays.

FDA reviewers characterized P304 as an adequate, event‑driven efficacy analysis with median follow‑up of about six months. FDA noted that the trial accrued 968 endpoint cases and that RVE was broadly consistent across age strata and high‑risk subgroups, with less precise estimates for influenza B because of small case counts. FDA's integrated safety review of more than 71,000 adults found higher rates of solicited local and systemic reactions (mostly grade 1–2, short duration) with mRNA‑1010 but similar rates of serious adverse events, adverse events of special interest and deaths overall. As FDA medical officer Dr. Brennan summarized, "Based on the totality of safety data, there are no important or identified potential risks beyond routine surveillance." The FDA also flagged a numerical imbalance in deaths within 28 days that it judged unlikely to reflect a vaccine‑related safety signal but recommended continued monitoring.

Committee discussion focused on three main themes: (1) whether event‑driven single‑season efficacy gives sufficient information about performance across seasons and against variable circulating viruses; (2) the higher reactogenicity profile and how to communicate it to clinicians and the public; and (3) special populations, especially very frail older adults and the immunocompromised, who were under‑represented in the pivotal efficacy dataset. The sponsor and FDA committed to a large randomized post‑licensure pragmatic study to compare mRNA‑1010 with enhanced vaccines in adults 65 and older; Moderna described plans for a trial enrolling roughly 400,000 older adults per season.

The committee vote closes the advisory portion of FDA's review; VRBPAC recommendations are nonbinding but carry significant weight in FDA's licensing decisions. The agency will complete its internal review and determine whether to grant traditional approval in adults 50–64 and accelerated approval in adults 65+, consistent with the regulatory framework discussed during the meeting. The agency and sponsor emphasized the importance of transparent post‑marketing surveillance and the agreed randomized pragmatic study as a condition of accelerated approval.