The U.S. Food and Drug Administration has approved Moderna’s mRNA-based seasonal influenza vaccine, making it the first messenger RNA flu shot authorized for use in the United States and marking another milestone for a technology that gained prominence during the COVID-19 pandemic.
The vaccine, marketed as mFlusiva, is approved for adults 50 years and older. The FDA granted traditional approval for adults aged 50 to 64 and accelerated approval for those 65 and older, with Moderna required to conduct additional studies to confirm clinical benefit in the older population.
The decision follows results from a late-stage clinical trial involving more than 40,000 participants, in which Moderna said the vaccine was 26.6% more effective at preventing influenza than a standard-dose seasonal flu vaccine. The company also reported stronger immune responses than Sanofi’s high-dose flu vaccine among older adults.
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Unlike traditional influenza vaccines, many of which are produced using egg-based manufacturing, mRNA vaccines can be updated more quickly to match circulating virus strains. Researchers have said the technology could allow manufacturers to respond more rapidly if influenza viruses evolve during a season. The approval expands Moderna’s portfolio beyond its COVID-19 vaccines and supports the company’s strategy of developing mRNA-based vaccines for multiple infectious diseases.
The FDA’s decision comes after a lengthy regulatory review. Earlier this year, the agency initially declined to proceed with Moderna’s application, citing questions about comparisons with high-dose influenza vaccines used in older adults. Following additional discussions and a unanimous recommendation from an independent advisory committee in June, the agency approved the vaccine.
The vaccine’s most commonly reported side effects were temporary injection-site pain, fatigue and fever, consistent with those seen with other mRNA vaccines. No major new safety concerns were identified during clinical trials.
Although the approval is effective immediately, Moderna is not expected to generate significant revenue from the vaccine until late 2027 because the company missed key contracting and purchasing cycles for the upcoming flu season. The approval could also support Moderna’s broader pipeline, including a future combination vaccine designed to protect against both influenza and COVID-19.
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Seasonal influenza causes millions of illnesses, hundreds of thousands of hospitalizations and thousands of deaths in the United States each year, according to federal health authorities. Public health officials continue to recommend annual flu vaccination, particularly for older adults and people at increased risk of severe disease.
With the FDA’s decision, mRNA technology is now being used against another major respiratory virus, potentially opening the door to faster vaccine development and more flexible responses to future influenza seasons.