FDA refuses to file Moderna’s seasonal flu vaccine application, citing comparator issue
By: IPP Bureau
Last updated : February 14, 2026 12:16 pm
The FDA’s Center for Biologics Evaluation and Research (CBER) cited Moderna’s choice of a licensed standard-dose flu vaccine as the comparator in its Phase 3 trial, saying it “does not reflect the best-available standard of care.”
Pharma powerhouse Moderna has announced that the U.S. Food and Drug Administration (FDA) has issued a Refusal-to-File (RTF) letter for its investigational seasonal influenza vaccine, mRNA-1010, halting the agency’s review.
The FDA’s Center for Biologics Evaluation and Research (CBER) cited Moderna’s choice of a licensed standard-dose flu vaccine as the comparator in its Phase 3 trial, saying it “does not reflect the best-available standard of care.” The letter, signed by Center Director Vinayak Prasad, did not raise any safety or efficacy concerns.
The RTF is at odds with prior FDA guidance. In April 2024, Moderna submitted its Phase 3 protocol to CBER, which indicated that using a licensed standard-dose comparator was acceptable, recommending only that vaccines preferred for adults over 65 could be considered.
“If you proceed with using a standard dose influenza vaccine comparator in participants ≥65 years of age, we agree with your plan to include statements in the Informed Consent Form,” CBER wrote. No objections were raised before the study began in September 2024.
Following the successful completion of its Phase 3 trials, which met all primary endpoints, Moderna held a pre-submission meeting with CBER in August 2025. The agency requested additional comparator analyses, which Moderna provided. “At no time in the pre-submission written feedback or meeting did CBER indicate that it would refuse to review the file,” the company noted.
“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,” said Stéphane Bancel, CEO of Moderna.
“It should not be controversial to conduct a comprehensive review of a flu vaccine submission that uses an FDA-approved vaccine as a comparator in a study that was discussed and agreed on with CBER prior to starting. We look forward to engaging with CBER to understand the path forward as quickly as possible so that America's seniors, and those with underlying conditions, continue to have access to American-made innovations.”