FDA Approves Moderna's mFLUSIVA, First mRNA-Based Flu Vaccine for Adults 50+
FDA approved Moderna's mFLUSIVA, the first mRNA-based flu vaccine for adults 50+. It was 27% more effective than standard flu shots in a large trial. The approval came after earlier FDA pushback.
The U.S. Food and Drug Administration on Wednesday approved the United States' first mRNA-based flu vaccine for adults 50 and older, drugmaker Moderna said. The vaccine, mFLUSIVA, was found to be about 27% more effective during the 2024–25 respiratory virus season than standard flu shots in Moderna's study, which enrolled over 40,000 adults 50 and older.
The approval came after initial pushback. In February, the FDA initially declined Moderna's request for review of the new flu vaccine, citing inadequate trials despite previous conflicting feedback within the agency. The FDA switched course about two weeks later and agreed to review the shot.
Side effects included injection-site reactions such as pain, tenderness and swollen lymph nodes; fatigue; headache; muscle or joint pain; nausea or vomiting; and fever.
Moderna says it expects to have the vaccine available this fall. For flu vaccines previously on the market, experts select flu strains for each fall's seasonal vaccines during the preceding February. Moderna's mRNA flu vaccine requires less time between strain selection and public circulation, which could allow for a closer match between the immunity conferred by vaccines and the season's circulating influenza strains.
In June, the FDA's independent vaccine advisory panel — made up of nine physicians and vaccine scientists — unanimously voted that the benefits of the new Moderna vaccine outweigh the risks. The panel endorsed the drugmaker's request for traditional approval for the vaccine in adults ages 50 to 64 and accelerated approval for adults 65 and older, which requires further trials to prove clinical benefit.
Typically, after a new vaccine is approved, the U.S. Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices will review data and weigh in on whether the agency should recommend it. However, a federal judge ruled in March that the HHS secretary did not follow federal legal procedures when he replaced all the committee's members, and it hasn't met since. The committee's next meeting is currently scheduled for October.
The approval comes despite the U.S. Department of Health and Human Services canceling 22 projects worth about $500 million focused on mRNA vaccine development in August 2025, with the HHS secretary claiming against evidence that "these vaccines fail to protect effectively against upper respiratory infections like COVID and flu." Moderna uses mRNA technology in its COVID-19 vaccines, as does drugmaker Pfizer, which also has mRNA-based flu vaccines in development. An mRNA-based vaccine from Moderna targeting both COVID-19 and the flu was approved in Europe earlier this year.