FDA approves Moderna’s first seasonal mRNA flu vaccine — full approval for 50–64, accelerated OK for 65+

The Food and Drug Administration has approved Moderna’s seasonal influenza vaccine, mRNA-1010, giving the company its first flu shot on the U.S. market — but not on identical terms for all older adults. The vaccine, branded mFLUSIVA, received traditional approval for adults ages 50 to 64 and accelerated approval for adults 65 and older, with the FDA requiring a post-marketing study to confirm clinical benefit in that older group.

The early August decision, publicly reported Aug. 5 and 6, marks a milestone for mRNA technology beyond COVID-19 and RSV. It also underscores the FDA’s more cautious approach for seniors, who face the highest risk from influenza and who already have other enhanced flu-shot options, including high-dose, adjuvanted and recombinant vaccines.

Moderna’s pivotal Phase 3 trial, known as Study P304, enrolled about 40,703 adults age 50 and older. In the trial’s prespecified primary analysis, mRNA-1010 showed about 26.6% relative vaccine efficacy compared with a licensed standard-dose flu vaccine against RT-PCR-confirmed influenza illness, meaning lab-confirmed cases identified by a standard molecular test.

The product is an mRNA lipid-nanoparticle seasonal flu vaccine. Regulatory and clinical materials describe it as a trivalent shot targeting three strains: influenza A/H1N1, A/H3N2 and B/Victoria.

For adults 65 and older, the FDA did not rely on direct clinical efficacy data in the same way. Instead, Moderna used immunogenicity data — evidence of the immune response the vaccine produced — comparing mRNA-1010 with Fluzone High-Dose, an established flu vaccine for older adults. FDA materials said mRNA-1010 met noninferiority and superiority criteria on several antibody endpoints, supporting accelerated approval rather than full approval for that age group.

That accelerated pathway comes with a condition. The FDA required a Phase 4 confirmatory study after launch to verify clinical benefit in adults 65 and older. Agency briefing materials describe that study as a large, pragmatic, active-controlled trial conducted across two flu seasons.

Safety data reviewed by the FDA and published in The New England Journal of Medicine showed that mRNA-1010 caused higher rates of expected short-term reactions than the standard-dose comparator. Those included injection-site pain, fever, headache, fatigue and myalgias, or muscle aches. But the FDA and the journal report said there were no major new safety signals.

The FDA’s vaccine advisory committee, the Vaccines and Related Biological Products Advisory Committee, voted 9-0 on June 18 that the vaccine’s benefits outweighed its risks for adults 50 and older.

The approval gives Moderna an entry into a crowded U.S. flu-vaccine market that has long been dominated by more traditional technologies. One argument for mRNA flu shots is speed: FDA and company materials have emphasized that mRNA platforms can be updated and manufactured faster than egg-based vaccines, a potential advantage when circulating flu strains shift.

At the same time, the split approval highlights the competitive and evidence-heavy landscape for vaccines aimed at seniors. Existing recommendations for older adults have historically favored enhanced products such as high-dose, recombinant or adjuvanted shots, making the FDA’s insistence on confirmatory evidence for mFLUSIVA in the 65-and-older population especially significant.

“Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America’s seniors,” Moderna CEO Stéphane Bancel said in a statement quoted by The Associated Press.