Moderna's First mRNA Flu Vaccine Launches This Season Despite Lingering Regulatory Fight
Moderna's mFlusiva, the first flu vaccine built on mRNA technology, the same platform used in the company's Covid-19 shots, is reaching pharmacies this fall for the 2026-2027 flu season after winning Food and Drug Administration approval. The approval rests on a late-stage trial of more than 40,000 adults across 11 countries, in which mFlusiva was found to be about 27 percent more effective than a standard-dose flu shot at preventing flu-like illness confirmed by lab testing. The FDA granted standard approval for adults 50 to 64 and accelerated approval for adults 65 and older.
The path to approval nearly collapsed in February 2026, when the FDA's biologics chief at the time, Vinay Prasad, issued a rare refusal-to-file notice declining to even review Moderna's application, objecting to the comparator vaccine used in the company's trial. The decision was reversed about two weeks later after Moderna publicly disclosed the dispute, and Prasad left the FDA at the end of April. The accelerated approval for adults 65 and older comes with a requirement that Moderna run an additional trial comparing mFlusiva against the high-dose flu shot the Centers for Disease Control and Prevention already recommends for that age group.
Health and Human Services Secretary Robert F. Kennedy Jr.'s department said he "has been clear that he believes mRNA products warrant heightened scientific scrutiny," and the vaccine entered the market carrying some of the strongest post-market study commitments the FDA has required. Moderna has said it does not expect mFlusiva to meaningfully contribute to revenue this season, since securing pharmacy contracts, insurance coverage, and a recommendation from the CDC's Advisory Committee on Immunization Practices (ACIP), the body that determines how new vaccines are used and covered, takes time. Side effects such as injection-site pain, fatigue, and headache were more common in the mFlusiva group during trials, though reported as mild to moderate.
What supporters say:
Public health researchers point to the 40,000-person trial showing mFlusiva outperformed a standard-dose shot, arguing a more effective vaccine matters given how many older adults are hospitalized with flu each year.
Backers of the mRNA platform say the technology lets manufacturers update vaccines to match circulating strains faster than older egg-based production methods.
Supporters argue the FDA's initial refusal to even review the application denied patients a potentially better option without a clear safety or efficacy justification.
What critics say:
Critics including HHS leadership argue mRNA vaccines deserve continued heightened scrutiny, pointing to the accelerated approval and required follow-up trial for seniors as evidence the data isn't yet settled for that age group.
Some skeptics object that mFlusiva was compared against a standard-dose shot rather than the high-dose version the CDC already recommends for people 65 and older, arguing that inflates the apparent benefit for the group most at risk from flu.
Skeptics note the unusual regulatory reversal, in which a sitting FDA official's refusal to review the application was overturned within weeks, and argue it raises questions about the integrity of the review process either way.
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#mRNA #FluVaccine #Moderna #FDA #PublicHealth
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