FDA Approves First mRNA Flu Vaccine for Adults 50 and Older

The US Food and Drug Administration has approved the nation’s first mRNA-based flu vaccine for adults 50 and older, giving older Americans another option for protection against influenza.

The vaccine, developed by Moderna and called mFlusiva, uses mRNA technology similar to that used in many COVID-19 vaccines. Instead of using an inactivated or weakened form of the flu virus, mRNA vaccines provide the body with instructions to produce a viral protein that triggers an immune response.

The vaccine received standard approval for adults ages 50 to 64 and accelerated approval for those 65 and older. Moderna will conduct an additional study in adults 65 and older to determine whether the vaccine’s stronger antibody response translates into better protection against illness.

In a company study involving more than 40,000 people over age 50, mFlusiva was about 27% more effective than standard flu vaccines during the 2024-25 flu season. However, participants experienced somewhat higher rates of side effects, including injection-site pain, muscle and joint pain, nausea, fever, headache and chills. Most reactions were mild to moderate and resolved within several days.

Experts say the vaccine could offer another advantage because mRNA vaccines can be produced more quickly than traditional flu vaccines. That could allow manufacturers to select vaccine strains closer to the start of flu season, potentially improving the match with circulating viruses.

The vaccine is expected to become available this fall, although supplies may initially be limited because pharmacies and clinics typically order flu vaccines months in advance. Insurance coverage also remains uncertain because federal vaccine advisers have not yet reviewed the new product.

Flu vaccination remains particularly important for older adults, who face a greater risk of hospitalization and serious complications from influenza.

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