TheChek News Flow

FDA Approves First mRNA Flu Vaccine in Win for Moderna After Arduous Review

Decision caps seven-month process that included rare refusal to consider shot

The Food and Drug Administration approved Moderna’s mRNA-based flu vaccine Wednesday for adults ages 50 and older, clearing the first shot of its kind after a review process that nearly collapsed in February.

The vaccine, called mFlusiva, uses the same messenger RNA technology as Moderna’s Covid-19 shots. It could reach pharmacies in time for the coming flu season, which typically starts in the fall.

Health Secretary Robert F. Kennedy Jr. has questioned mRNA vaccine technology, and the Department of Health and Human Services canceled about $500 million in mRNA research contracts last year in moves that public-health officials questioned as politically motivated rather than rooted in science.

In February, the FDA initially refused to review Moderna’s application at all, a rare move signed by the agency’s then head of vaccine development, Vinay Prasad, who has left the agency. Prasad cited the fact that Moderna tested its experimental vaccine for seniors measuring case counts against a standard-dose flu shot rather than Fluzone High-Dose, the version the FDA normally recommends for that age group.

Moderna was surprised by the FDA’s decision in February. “It does feel like the rules of the game are being changed after it’s been played,” Moderna President Stephen Hoge said at the time.

The agency reversed course days later after Moderna proposed a revised plan that included another trial.

In June, an FDA advisory committee voted unanimously to recommend mFlusiva for adults 50 and older.

Even with FDA approval, the vaccine’s commercial prospects are uncertain. The Centers for Disease Control and Prevention panel that makes national vaccine recommendations remains tied up in litigation after Kennedy replaced its members last year with some outspoken vaccine opponents and a federal judge ruled most of his appointees were unqualified to serve. Doctors and insurers face uncertainty over whether mFlusiva will be recommended only for specific people such as those who are immunocompromised.

Wall Street doesn’t expect the vaccine to generate meaningful sales until the 2027-28 flu season because commercial contracting for seasonal flu shots takes place earlier in the year. The company said it expects to have mFlusiva available for eligible populations in the U.S. for the 2026-27 season.

Traditional flu shots are grown in chicken eggs, a process that takes about six months and forces manufacturers to guess months in advance which strains will circulate. Moderna’s mRNA shot can be made in as little as two to three months, meaning it could better match the actual virus once flu season arrives.

In a study of more than 40,000 adults, mFlusiva cut the risk of flu by 26.6% compared with a standard-dose vaccine. That reduction was 47.9% against flu severe enough to send patients to the hospital or urgent care.

For adults 65 and older, Moderna has tested the shot against Fluzone High-Dose and found its shot generated a stronger antibody response in blood tests. That trial was designed to measure antibody levels rather than tracking flu infections, so Moderna wasn’t able to produce a head-to-head case count against Fluzone High-Dose. That gap is why regulators have required a follow-up study, which Moderna said will enroll up to 800,000 people over two flu seasons.

The approval is a building block for a combination mRNA Covid-flu shot, which the company pulled from review last year after the FDA requested additional flu data.