Moderna FDA Refusal to File Stalls Flu Vaccine
Moderna FDA Refusal to File cites a comparator dispute and could spur biotech volatility while prompting reassessment of vaccine regulatory risk.
KEY TAKEAWAYS
- CBER issued a Refusal-to-File for Moderna's mRNA-1010 BLA over a comparator dispute.
- Phase 3 trials met prespecified superiority endpoints across two pivotal studies with combined 43,808 participants.
- Moderna said the RTF cited no safety or efficacy concerns and would not alter 2026 guidance.
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Moderna (MRNA) said the FDA issued a Refusal to File (RTF) on Feb. 10, 2026, for its Biologics License Application (BLA) for mRNA-1010 after the FDA’s Center for Biologics Evaluation and Research (CBER) found the trial comparator did not reflect the "best-available standard of care." The company said the setback will not affect its 2026 guidance.
FDA Refusal and Phase 3 Data
CBER’s refusal cited the use of a licensed standard-dose influenza vaccine as the comparator, which it said failed to meet the "adequate and well-controlled" requirement under 21 C.F.R. § 314.126. The agency did not raise any safety or efficacy concerns. The RTF letter, signed by CBER Director Vinay Prasad, MD, MPH, was posted in full on Moderna’s website. Moderna announced the RTF in a press release at 6:00 p.m. ET on Feb. 10.
mRNA-1010 is Moderna’s investigational seasonal influenza vaccine using mRNA technology. Its Phase 3 program included two pivotal trials: P303, which compared safety and immunogenicity against a high-dose comparator in participants 65 and older, and P304, which assessed safety and relative efficacy versus a standard-dose comparator in participants 50 and older. Both trials met their pre-specified primary endpoints of statistical superiority, enrolling a combined total of 43,808 participants. The P304 trial began in September 2024 following a protocol reviewed by CBER.
In an April 2024 pre-Phase 3 consultation, CBER accepted the use of a licensed standard-dose comparator and recommended a high-dose comparator for older adults. At an August 2025 pre-submission meeting, the agency requested supportive comparator analyses but did not indicate a refusal to file. Moderna said it provided the requested analyses and argued the RTF conflicts with prior agency feedback and past vaccine approvals that used similar standard-dose comparators such as Fluzone HD, Fluad, and Flublok.
Guidance, Next Steps, and International Review
Moderna said the RTF will not affect its 2026 financial guidance. The company exercised a Priority Review Voucher for the U.S. filing and has requested a Type A meeting with CBER to address the procedural concerns.
The BLA remains under review in the European Union, Canada, and Australia, with additional regulatory submissions planned for 2026. Moderna cited the earliest potential approvals as late 2026 or early 2027, contingent on those ongoing reviews.
"This decision by CBER, which did not identify any safety or efficacy concerns with our product, does not further our shared goal of enhancing America's leadership in developing innovative medicines," Moderna CEO Stéphane Bancel said.
