mRNA Enters Annual Flu Vaccination: FDA Approves Moderna Vaccine for Adults Aged 50 and Older

Flu vaccines have to be reformulated almost every year, yet they have long relied on traditional manufacturing processes such as egg-based or cell-based production. The U.S. Food and Drug Administration (FDA) has approved Moderna’s mFLUSIVA (mRNA-1010), bringing mRNA technology into the U.S. seasonal flu vaccine market for the first time and extending the platform into the regular, recurring setting of annual vaccination.

The approval covers adults aged 50 and older, but the two age groups followed different regulatory pathways: full approval was granted for adults aged 50 to 64, while accelerated approval was granted for those aged 65 and older. Moderna must conduct further research to confirm the vaccine’s actual clinical benefit in older adults. The company said the first products are expected to be available through select retail channels during the 2026–2027 flu season.

The key evidence came from a late-stage trial involving more than 40,000 adults aged 50 and older, conducted during the 2024–2025 Northern Hemisphere flu season. Laboratory-confirmed flu cases occurred in about 2.0% of mFLUSIVA recipients and 2.8% of recipients of a conventional standard-dose vaccine, translating to a relative vaccine efficacy of 26.6%; among participants aged 65 and older, relative efficacy was 27.4%. This represents a relative reduction in case risk of about one-quarter and should not be interpreted as meaning that the vaccine can prevent nearly 90% of flu cases.

The trial also left important comparative limitations. In the United States, adults aged 65 and older already have preferentially recommended options, including high-dose, adjuvanted, and recombinant flu vaccines, but the large efficacy trial used a standard-dose vaccine as the comparator. A separate study in older adults compared antibody responses with those from an approved high-dose vaccine, supporting accelerated approval; whether this translates into an equivalent reduction in actual disease remains to be answered by confirmatory research.

Safety data did not reveal major new warning signs, but short-term reactions were more common with mFLUSIVA, including injection-site pain, fever, headache, fatigue, and muscle aches. Most were temporary and mild to moderate. For a vaccine that may be administered every year, postmarketing surveillance will need to assess not only rare adverse events but also whether greater reactogenicity affects public acceptance.

Background

The potential advantage of the mRNA platform is that it does not require cultivation of the whole virus and could theoretically shorten the time needed to adjust vaccine design and production in response to annually changing flu strains. However, this trial demonstrated protection relative to a standard-dose vaccine during a specific flu season; it did not directly establish whether faster reformulation could improve strain matching. The approval is therefore a milestone marking the platform’s entry into the seasonal vaccine market, but it does not represent a comprehensive victory over all existing flu vaccines for older adults.