The U.S. Food and Drug Administration has declined to review Moderna’s application for a novel flu vaccine using mRNA technology. Moderna disclosed receiving a “refusal-to-file” letter from the agency, highlighting ongoing rigorous evaluation of mRNA-based vaccines under Health Secretary Robert F. Kennedy Jr.
Reasons for FDA’s Refusal
FDA vaccine director Dr. Vinay Prasad issued the letter, stating the application lacks an “adequate and well-controlled trial.” The objection centers on Moderna’s 40,000-participant study, which compared the new vaccine to a standard flu shot rather than the top standard of care available in the U.S. during the trial period.
The letter references 2024 guidance from FDA officials, which Moderna partially disregarded. While the agency deemed the chosen standard-dose shot acceptable overall, it recommended a high-dose version preferred for adults aged 65 and older. Moderna maintains the FDA approved proceeding with the original plan.
Clinical Trial Results and Additional Data
The trial demonstrated superior effectiveness of the mRNA vaccine in adults aged 50 and older compared to the standard shot. Moderna also submitted data from a separate study against a licensed high-dose flu vaccine for seniors.
“The FDA did not identify any safety or efficacy concerns with our product,” stated Moderna CEO Stephane Bancel.
Moderna’s Next Steps and Global Applications
Such refusals to file are uncommon, especially for new vaccines following extensive pre-submission talks. Moderna has requested an urgent meeting with the FDA and pursued approvals in Europe, Canada, and Australia.
Broadened FDA Scrutiny on mRNA Vaccines
Under Kennedy’s leadership, the FDA has intensified oversight of mRNA technologies, which he has questioned publicly. Recent moves include revising COVID-19 vaccine recommendations, adding warnings to leading mRNA COVID shots, and reshaping advisory panels by removing certain critics.
Kennedy’s department previously terminated over $500 million in mRNA vaccine development funding. Additionally, the FDA ended streamlined annual flu vaccine updates based on immune response data alone, as outlined in an internal memo by Prasad. This shift drew criticism from more than a dozen former FDA commissioners.
