Moderna said the FDA refused to file (refuse‑to‑file) its application for an mRNA influenza vaccine, citing trial design issues centered on the comparator used in the pivotal study rather than explicit safety or efficacy deficits. Moderna disputed the agency’s rationale, arguing the study design had prior agency feedback and that the comparator choice met regulatory standards. Moderna has asked for a meeting to clarify the path forward. The company noted positive Phase 3 efficacy readouts previously reported but warned the refusal will delay its standalone flu program and combination vaccine plans. Agency leadership at CBER signaled tighter expectations for vaccine trial comparators under recent FDA management. The move triggered a share decline and intensified debate over evolving regulatory expectations for vaccine trials and comparator standards, particularly for mRNA platforms seeking expanded indications.