Biotechnology company Moderna announced that the U.S. Food and Drug Administration (FDA) has declined to review its application for an mRNA-based seasonal influenza vaccine, a decision that could delay the company’s plans to expand beyond COVID-19 immunizations.
According to the company, regulators issued a refusal-to-file notice, indicating the submission was not sufficiently complete for a formal review. Such notices typically mean additional data, documentation or clarification is required before the agency can begin evaluating safety and effectiveness. Moderna said it intends to work with the FDA to address the concerns and resubmit the application.
The experimental vaccine is part of Moderna’s broader strategy to apply its mRNA technology platform to multiple respiratory diseases. The company has been developing a combined respiratory pipeline, including vaccines targeting influenza, COVID-19 and RSV. Approval of a flu shot would mark a major step in diversifying its product portfolio following the decline in pandemic-era vaccine demand.
Industry analysts say regulatory caution around newer technologies may lead to more detailed data requirements, particularly for seasonal vaccines administered to large populations annually. While mRNA vaccines proved effective during the COVID-19 pandemic, influenza presents additional challenges due to constantly evolving virus strains and the need for consistent performance across multiple seasons.
Moderna emphasized that the FDA’s decision does not represent a rejection of the vaccine’s safety or efficacy but rather a procedural step requiring more information. The company expects to continue discussions with regulators in the coming months.
If eventually approved, the mRNA flu vaccine could potentially offer faster updates to match circulating strains compared with traditional egg-based manufacturing methods. However, the timeline for review now depends on how quickly the requested data can be provided and accepted by the regulator.
