America's First mRNA Flu Shot Gets FDA Approval After a Rocky Road

A Historic Approval — and a Turbulent Path to Get There

The Food and Drug Administration has approved a first-of-its-kind flu vaccine made with messenger RNA technology, enabling its developer, Moderna, to complete a dramatic regulatory turnaround. The vaccine, called mFlusiva, represents the same foundational platform that powered the COVID-19 vaccines — now applied to one of the most persistent seasonal health threats Americans face every year. But the road to approval was anything but smooth.

In a move that seemed out of reach just six months ago, the FDA approved Moderna's influenza vaccine for older adults on August 5 — the first licensed flu shot made using messenger RNA technology. In February, Vinay Prasad, the FDA's head of biologics at the time, overturned the recommendation of career staff and issued a rare "refusal-to-file" notice to the company, saying the agency wouldn't review the vaccine based on the available data package. The letter was signed personally by Prasad, which is not how such letters normally leave the building. His sole objection was that Moderna had tested the vaccine against a standard-dose flu shot rather than the high-dose version preferred for people over 65 — a criterion that appears nowhere in the agency's own influenza guidance, and one that Prasad's own center had told Moderna in writing was acceptable.

Regulators in Europe, Canada, and Australia had accepted the identical application without difficulty. Fifteen days later, after one meeting and a public outcry, the FDA reversed itself, agreed to review the file, and set the decision date for August 5. Nothing about the evidence changed in those 15 days.

What the Science Actually Shows

The new vaccine 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. That's a meaningful jump in protection for a disease that kills tens of thousands of Americans in a bad year. No new or serious safety concerns were identified by either Moderna or FDA staff reviewers, though adverse reactions consistent with mRNA vaccines — such as fatigue, joint pain, and muscle aches — were recorded in the trial.

The FDA's Vaccines and Related Biological Products Advisory Committee voted 9-0 that the benefits of mFlusiva outweigh its risks for adults aged 50 to 64, and separately 9-0 for adults aged 65 and older at a June 18, 2026 advisory committee meeting. The FDA granted approval for two age groups — adults 50 to 65 and adults 65 and up — on the condition that Moderna run an additional clinical trial in the older group.

Why the Technology Matters Beyond This Flu Season

Currently, it takes six months to create flu vaccines because they require growing the influenza virus in eggs before processing it into the vaccine. With mRNA technology, the shot takes just six weeks to develop. The mRNA vaccine will make it possible to rapidly adjust to new strains of the virus, something health specialists have been unable to do in the past.

For adults 65 and older, Moderna has agreed to conduct a Phase 4 post-licensure trial to gather more effectiveness data, looking in particular at how the vaccine compares to existing high-dose or adjuvanted vaccines recommended for that older age group. Having a licensed mRNA seasonal flu vaccine could also speed up the licensure pathway for a pandemic flu vaccine, if the need arose.

Political Headwinds Still Loom

The approval comes despite repeated criticism of mRNA technology by Health and Human Services Secretary Robert F. Kennedy Jr., who last year canceled 22 vaccine development projects that use mRNA technology. Prasad, who has since left the agency, is a supporter of Kennedy, an outspoken critic of vaccines and mRNA technology — and vaccine pushback remains widespread within the Trump administration.

mFlusiva must still move through the Centers for Disease Control and Prevention's recommendation process before it is likely to receive routine insurance coverage. The vaccine is expected to be available commercially in the U.S. within the next few weeks, in time for the 2026–2027 flu season, although it may have missed the procurement window for some health systems. Whether political resistance translates into obstacles at the CDC recommendation stage — the gateway to broad insurance coverage and widespread use — may ultimately determine how many Americans actually benefit from this breakthrough this fall.