FDA punts on Moderna’s mRNA flu shot as vaccine policy heat rises

CNBC, CNN, FOX News, and the New York Times contributed to this report.

Moderna says the FDA has refused to even start reviewing its application for an mRNA flu vaccine — a blunt “refusal-to-file” that could push back US access to a shot the company pitched as stronger for older adults.

The agency didn’t flag safety or effectiveness problems, according to Moderna — its gripe was about trial design. Regulators said the Phase 3 study used a standard-dose flu vaccine as the comparator, which they argued “did not reflect the best-available standard of care,” and therefore didn’t meet their bar for an “adequate and well-controlled” trial. Moderna counters that the trial plan had been discussed with the agency and that it added the extra analyses FDA asked for.

Moderna’s chiefs were blunt. CEO Stéphane Bancel and company president Dr. Stephen Hoge said the RTF wasn’t about safety or efficacy and that the decision contradicts earlier feedback the company got from FDA staff. Moderna has requested a meeting to figure out a way forward and said reviews are still underway in Europe, Canada and Australia.

This isn’t happening in a policy vacuum. The move comes as the Biden administration’s Health Department — now led by Robert F. Kennedy Jr. — has shaken up vaccine oversight, drawing fresh scrutiny on mRNA shots and prompting changes to advisory panels and funding decisions. That broader shift has made the vaccine-approval landscape noticeably bumpier for companies working on COVID and flu mRNA candidates.

The refusal letter was signed by the head of the FDA’s vaccine shop, Vinay Prasad, who’s signalled tougher standards on vaccines since stepping into the role. His stance — and other recent agency moves — have sparked pushback from industry and investors, who warn that shifting rules and “decisional volatility” could chill innovation.

Practically, the RTF will slow Moderna’s U.S. timeline. The company had reported positive Phase 3 results showing better performance than the comparator in adults 50+, and it had been positioning the shot as a building block for combo vaccines that pair flu and COVID protection. Now, US approval looks delayed while Moderna and regulators hash out what counts as an appropriate comparator and acceptable trial design.

Investors reacted fast: Moderna shares slipped after the news, underscoring how much market value is tied to each regulatory step for next-gen vaccines.

Bottom line: Moderna insists its data are solid and says the FDA’s move is inconsistent with earlier guidance; the agency says the trial didn’t meet current standards for control arms. Either way, the episode highlights how political winds and new regulatory preferences are reshaping the path for mRNA vaccines — and could make it tougher to get future shots across the finish line in the US.