The FDA refused to review Moderna’s mRNA flu vaccine application February 10, requiring the company to conduct proper trials instead of comparing its experimental shot to standard flu vaccines. Moderna complained the FDA changed the rules. The real issue: mRNA technology got fast-tracked for COVID without adequate testing, and Moderna wants the same shortcuts for seasonal flu.
Vinay Prasad, the FDA’s top vaccine official, overruled career scientists who were ready to proceed. Three FDA officials told STAT News that reviewers supported moving forward. David Kaslow, head of the vaccine office, wrote a memo recommending review. Prasad rejected the application anyway.
The February 3 letter cited no safety or efficacy concerns. Instead, Prasad wrote the trial design wasn’t adequate because Moderna compared its mRNA shot to standard flu vaccine instead of high-dose shots for people over 65—the population most at risk.
Moderna claims the FDA approved the trial design 18 months ago before Phase 3 began. Christopher Ridley, Moderna’s spokesperson: “The FDA reviewed and cleared the trial design as adequate before the study began.” The company posted Prasad’s rejection letter publicly—an unusual step signaling frustration.
At a February 11 press conference, an FDA official repeatedly described the prior position as a “strong recommendation” rather than a requirement. The official characterized the rejection as “procedural rather than substantive” and said “a refusal to file is not a rejection of the drug.”
HHS spokesperson Andrew Nixon offered a different version: “The FDA rejected Moderna’s application because the company refused to follow very clear guidance.” That contradicts Moderna’s documentation showing FDA approval before the company spent 18 months conducting the study.
In May 2025, HHS Secretary Robert F. Kennedy Jr. ordered that all new vaccines require placebo-controlled trials. Medical ethics typically prohibit placebo trials when effective vaccines exist—it leaves trial participants vulnerable when safe vaccines could protect them. But it also means new vaccines never get tested against inert substances, only against existing vaccines that may themselves have safety issues.
Kennedy’s order addressed a problem with mRNA COVID vaccine approval. Those shots got authorized under emergency use without long-term placebo-controlled safety data. The FDA compared them to nothing, approved them fast, and distributed them to billions worldwide. Safety signals emerged—myocarditis, blood clots, neurological issues—but comprehensive placebo-controlled trials never happened.
Now Moderna wants to use the same mRNA technology for flu shots using the same approval pathway: compare to existing vaccines, skip rigorous testing, get fast authorization.
Prasad has overruled FDA career staff before. Last summer he “basically overruled two different internal FDA expert panels” on COVID vaccines. The pattern: career scientists ready to approve mRNA products quickly, Prasad requiring actual safety evidence first.
The pharmaceutical industry reacted predictably. Dr. Peter Hotez said he saw “no obvious scientific basis” for the new requirements. Bloomberg called it “regulatory chaos.” Multiple outlets reported “vaccine skepticism seeping into the FDA from the top.”
But seasonal flu isn’t a pandemic. There’s no emergency. Traditional flu vaccines exist. If Moderna’s mRNA flu shot is actually better, it can prove that in trials designed to show superiority to the best available standard of care.
The fight isn’t about trial design technicalities. It’s about whether mRNA technology gets permanent fast-track status based on emergency COVID authorizations, or whether it meets the same safety standards as every other pharmaceutical product.
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