The United States has its first mRNA-based influenza vaccine. The Food and Drug Administration approved Moderna’s mFLUSIVA on Wednesday for adults aged 50 and older, marking the entry of the same messenger RNA technology used in COVID-19 vaccines into mainstream annual flu protection.
The vaccine was found to be approximately 27% more effective during the 2024-25 respiratory virus season than standard flu shots, based on a Moderna study enrolling more than 40,000 adults 50 and older. Moderna CEO Stéphane Bancel said the approval “reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation.” The company expects mFLUSIVA to be available this autumn.
What Makes mRNA Flu Vaccines Different
The technology at the core of mFLUSIVA is the same platform Moderna and Pfizer used to develop COVID-19 vaccines at record speed. Traditional flu vaccines require manufacturers to grow influenza virus strains — a process that takes months and requires strain selection to happen in February, roughly eight months before the flu season peaks.
mRNA vaccines can be designed and produced more quickly, compressing the time between identifying circulating strains and manufacturing a matched vaccine. In practical terms, this means an mRNA flu shot could more accurately reflect the actual viruses circulating each winter rather than strains predicted months in advance — a long-standing limitation of conventional flu vaccine development.
Who Can Get It, and What Are the Side Effects
The FDA approval covers adults aged 50 and older. Within that group, the agency granted traditional approval for the 50-64 age bracket and accelerated approval for adults 65 and older — the latter requiring additional trials to confirm clinical benefit over time.
Reported side effects are consistent with those of other vaccines and include injection-site reactions such as pain, tenderness, and swollen lymph nodes; fatigue; headache; muscle or joint pain; nausea or vomiting; and fever.
A Contested Approval in a Complicated Political Environment
The path to approval was not straightforward. In February, the FDA initially declined to review Moderna’s application, citing inadequate trial data — before reversing course approximately two weeks later and agreeing to proceed. In June, the FDA’s independent vaccine advisory panel, composed of nine physicians and vaccine scientists, unanimously voted that the benefits of mFLUSIVA outweigh its risks and endorsed the approval request.
The approval comes in political tension with the Trump administration’s posture on mRNA technology. Despite the record-speed mRNA COVID-19 vaccine development being a credited achievement of Trump’s first term, his second administration cancelled 22 mRNA vaccine development projects worth approximately $500 million in August 2025. HHS Secretary Robert F. Kennedy Jr., in announcing those cancellations, claimed without scientific basis that mRNA vaccines “fail to protect effectively against upper respiratory infections like COVID and flu.” The FDA’s approval of mFLUSIVA runs directly counter to that position.
The approval also arrives with one important gap in the standard rollout process. Typically, the CDC’s Advisory Committee on Immunization Practices reviews new vaccines after FDA approval and weighs in on whether the agency should formally recommend them for use. However, that committee has not met since a federal judge ruled in March that Kennedy failed to follow federal legal procedures when he replaced all its members. Its next scheduled meeting is October — meaning formal CDC guidance on mFLUSIVA may not arrive until after the vaccine is already available to the public.
Moderna’s mRNA vaccine targeting both COVID-19 and influenza simultaneously received EU approval earlier this year. Pfizer also has mRNA-based flu vaccines in clinical development.
This article discusses a newly approved vaccine. If you have questions about whether mFLUSIVA or any flu vaccine is appropriate for you, please speak with your healthcare provider.
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