Moderna received a refusal-to-file letter from the FDA for its mRNA influenza vaccine application, and company executives expressed surprise at the agency’s decision. Moderna said it had submitted extensive supporting analyses requested in prior discussions; FDA staff later raised concerns about comparator selection in the pivotal trial. Stat interviews with Moderna leadership described the refusal as abrupt and disruptive to large respiratory vaccine programs. The regulatory action has rippled across the sector, prompting public debate about shifting FDA expectations under new leadership and signaling greater scrutiny of trial design and comparator strategy in vaccine submissions. Industry executives warn that the decision could chill investment in U.S. vaccine development.