FDA Approves Moderna’s mRNA Flu Vaccine, a First
The U.S. Food and Drug Administration has approved Moderna’s mRNA-based influenza vaccine, mFLUSIVA, marking the first time a flu shot made with messenger RNA technology has received regulatory approval anywhere in the world. The vaccine is approved for adults aged 50 and older and represents a significant departure from traditional egg-based flu vaccines.
Moderna, based in Cambridge, Massachusetts, announced the approval on Wednesday, saying the FDA granted full approval for mFLUSIVA’s use in people ages 50 to 64 based on a study of 40,000 people that found 27% fewer flu cases among those who received the new shot compared with those who got a different common flu vaccine brand. For people 65 or older, the FDA granted accelerated approval based on a smaller study showing the shot generated a strong immune response compared with an existing high-dose vaccine for seniors, while Moderna conducts an additional confirmatory study, according to AP News.
A New Era for Flu Prevention
The approval is a landmark moment for vaccine technology. mRNA vaccines work by delivering instructions to cells to produce proteins that trigger an immune response—the same Nobel Prize-winning platform used in Moderna’s COVID-19 vaccines. Traditional flu vaccines, by contrast, are grown in fertilized chicken eggs, a process that requires six to eight months for production. mRNA vaccines can be produced in one to two months, offering significant advantages in responding to rapidly mutating flu strains, as Ars Technica reported.
The need for better flu protection is substantial. During the 2024–2025 season, more than 45,000 Americans died from influenza. People 65 and older account for an estimated 70–85% of flu-related deaths and 50–70% of flu-related hospitalizations, despite making up less than 20% of the U.S. population, according to Moderna’s IR Insights.
Moderna’s data showed no major safety issues, although the shot did cause some temporary reactions including injection site pain, fever, headache, tiredness, and aches that occurred somewhat more frequently than with today’s flu shots. Most side effects were mild and lasted two days or less.
A Rollercoaster Path to Approval
The approval caps a highly unusual and contentious review process. In February, Vinay Prasad, then the FDA’s head of biologics, overturned the recommendation of career staff and issued a rare “refusal-to-file” notice, saying the agency would not review the vaccine based on the available data package, as STAT News reported. Prasad argued that Moderna didn’t compare its mRNA vaccine’s efficacy to the correct existing vaccine, despite FDA officials having previously signed off on the trial designs.
Moderna publicly challenged the ruling, releasing the FDA’s letter and issuing a strongly worded statement from CEO Stéphane Bancel, who said the decision “does not further our shared goal of enhancing America’s leadership in developing innovative medicines.” Two weeks later, the FDA reversed course and agreed to review the application. Prasad left the agency at the end of April amid a series of controversial and widely decried moves.
The controversy reflected heightened vaccine scrutiny under Health Secretary Robert F. Kennedy Jr., who has been openly hostile to mRNA vaccines. In August 2025, the Department of Health and Human Services canceled 22 mRNA vaccine development projects worth roughly $500 million and ordered a halt to federal investment in the platform, as STAT’s First Opinion noted. Kennedy claimed the data showed these vaccines fail to protect effectively, a position contradicted by the unanimous vote of FDA advisors in June who determined mFLUSIVA’s benefits outweigh its risks for adults 50 and older.
What This Means for Flu Season
Moderna expects mFLUSIVA to be available at select retailers for the 2026–2027 flu season. Bancel celebrated the approval, saying it “demonstrates the continued strength and versatility of our mRNA platform.”
“Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America’s seniors,” he said. “This approval also reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation.”
Beyond the U.S., regulatory submissions are under review in the European Union, Canada, and Australia, with additional submissions planned later in 2026.
Remaining Uncertainties
Despite the approval, significant questions remain. The CDC’s Advisory Committee on Immunization Practices (ACIP)—the panel that makes recommendations for federal vaccine policy—is effectively defunct due to litigation over Kennedy’s appointments. In March, a federal judge ruled that most of the anti-vaccine allies Kennedy had installed onto the advisory panel were unqualified, ordering a temporary injunction reversing their appointments. The Trump administration is appealing, and the panel has not met amid the litigation, as The Guardian reported.
Without an ACIP recommendation on mFLUSIVA’s clinical use for the quickly approaching flu season, doctors face uncertainty about which adults over 50 should be recommended to use the vaccine. It’s also unclear if mFLUSIVA will be covered by federal vaccine programs or private insurance companies, which are required to cover ACIP-recommended vaccines.
Wall Street is not expecting meaningful sales until the 2027–2028 season, according to STAT News.
Looking Ahead
The approval validates the mRNA platform beyond COVID-19 and opens the door for more rapid and adaptable flu vaccines. The ability to produce flu vaccines in one to two months—versus six to eight months for egg-based vaccines—could be transformative for responding to pandemic influenza threats.
Moderna now has approved products spanning COVID-19, RSV, and influenza, plus a COVID+Flu combination vaccine approved in Europe. As the company builds its respiratory franchise, the scientific community will be watching closely to see how mFLUSIVA performs in real-world use, whether the confirmatory study for adults 65 and older confirms clinical benefit, and how quickly international regulators follow the FDA’s lead.
For now, the approval represents a triumph of scientific review processes over political interference—and a new chapter in the fight against a virus that continues to claim tens of thousands of American lives each year.