The U.S. Food and Drug Administration issued a refusal-to-file (RTF) letter for Moderna’s mRNA influenza vaccine candidate mRNA-1010, and Moderna publicly disputed the agency’s rationale. The FDA cited deficiencies in Moderna’s pivotal trial design rather than safety or efficacy concerns, a move Moderna says contradicts prior guidance the company received during development. Moderna has requested a Type A meeting to define a path forward; the company noted regulatory authorities in the EU, Canada and Australia accepted the filing for review. Vinay Prasad, director of CBER, signed the RTF letter and is named in agency communications as driving the decision; industry sources report internal disagreement within FDA review teams. Refusal-to-file means the agency will not begin a formal review of the submission until specified deficiencies are addressed. Moderna emphasized its large Phase 3 dataset and said it will seek clarification from the agency while other regulators proceed with review.