Biotechnology company Moderna, Inc. said the FDA Center for Biologics Evaluation and Research has refused to begin reviewing its biologics license application for the investigational influenza vaccine mRNA-1010, issuing a Refusal-to-File letter despite no identified safety or efficacy concerns.
According to the company, regulators rejected the submission because the Phase 3 trial used a licensed standard-dose seasonal flu vaccine comparator rather than what the agency described as the “best-available standard of care.” Moderna noted that existing regulations governing well-controlled studies do not specifically require such a comparator and that prior written communications from the agency had permitted the chosen study design.
The dispute centers on earlier regulatory guidance. In 2024, before the late-stage study began, the agency reviewed the protocol and indicated a standard-dose comparator would be acceptable, while recommending certain vaccines for older adults. The company proceeded accordingly and completed the trial in 2025, meeting all primary endpoints. During a pre-submission meeting, regulators requested additional analyses comparing the vaccine with a high-dose influenza shot — which Moderna says it provided — but did not warn the filing would be refused.
Chief executive Stephane Bancel criticized the decision, arguing that a full review should occur when a study uses an already approved vaccine comparator and meets pre-agreed trial criteria. The company has requested a Type A meeting with regulators to clarify the path forward.
The investigational vaccine is part of Moderna’s broader respiratory franchise, which aims to expand beyond COVID-19 vaccines into combination and seasonal immunizations. The company emphasized that the refusal does not relate to clinical performance of the product and therefore does not affect its 2026 financial outlook.
Outside the United States, the regulatory picture differs. The vaccine application is under review in Europe, Canada and Australia, and additional filings are planned in 2026. Moderna estimates potential approvals in those regions could begin in late 2026 or early 2027, depending on review timelines.
Industry analysts say Refusal-to-File letters are uncommon but typically procedural, meaning the agency declines to assess the application until specific requirements are addressed. The outcome will likely determine whether the company must conduct another study or resubmit additional comparative data before the vaccine can be considered for approval in the U.S. market.