FDA Issues Refusal-to-File Letter
The U.S. Food and Drug Administration (FDA) has declined to review Moderna’s application for a new mRNA-based flu vaccine. The company said the refusal could slow the rollout of a vaccine aimed at providing better protection for older adults.
Moderna received a “refusal-to-file” (RTF) letter from the FDA’s Center for Biologics Evaluation and Research (CBER). The letter cited the company’s Phase 3 trial design, saying it lacked a “comparator arm” that reflects the best-available standard of care.
Moderna Responds to FDA Decision
Moderna CEO Stéphane Bancel emphasized that the FDA did not raise concerns about the safety or effectiveness of the vaccine. He said the decision “does not further our shared goal of enhancing America’s leadership in developing innovative medicines.”
Bancel criticized the move, noting that the company had conducted the study with an FDA-approved comparator vaccine that was agreed upon with CBER before the trial began. He said Moderna plans to work with the FDA to clarify the next steps.
Context: Vaccine Oversight Under RFK Jr.
The refusal comes amid heightened scrutiny over vaccine approvals under Health Secretary Robert F. Kennedy Jr., who has questioned mRNA vaccines and rolled back certain COVID-19 vaccine recommendations. Over the past year, Kennedy removed members of the federal vaccine advisory panel, appointed new ones, and canceled $500 million in mRNA vaccine contracts.
The FDA recently authorized COVID-19 vaccines only for high-risk groups and removed them from routine immunization schedules for healthy children and pregnant women.
Details on the Phase 3 Trial
The FDA’s objection focused on Moderna’s choice of comparator: a licensed standard-dose seasonal flu shot. While guidance in 2024 suggested a standard-dose comparator would be acceptable, the FDA argued a higher-dose vaccine would better reflect the “best-available standard of care” for adults over 65.
Moderna stated that the FDA raised no objections to the trial’s design before it began in September 2024. The company also said it provided additional analyses requested by CBER during submission.
Next Steps
Moderna has requested a Type A meeting with CBER to discuss the RTF decision. Meanwhile, regulatory reviews for the vaccine continue in Canada, the European Union, and Australia.
