The U.S. Food and Drug Administration approved Moderna's mFLU-SIVA, the first mRNA-based seasonal influenza vaccine for adults aged 50 and older [1, 3].
This approval represents a significant shift in vaccine technology, moving the mRNA platform beyond COVID-19 and into the annual fight against the flu. The decision follows a period of regulatory tension and a rare reversal by the agency.
The vaccine, known technically as mRNA-1010, is approved for different age groups under different regulatory paths. The FDA granted full approval for adults aged 50 to 64, and accelerated approval for those aged 65 and older [1].
The path to authorization was not linear. The FDA initially refused to review Moderna's application due to concerns regarding the clinical trial data and the comparator vaccine used in the study [1, 4]. However, the agency reversed this decision after Moderna addressed those concerns, concluding that the benefits of the vaccine outweigh the potential risks [1, 4].
Clinical data played a central role in the review process. A phase 3 trial for the vaccine showed a 26.6% relative vaccine efficacy [2]. Despite this figure, the FDA determined the product met the necessary standards for authorization in time for the 2026 season [3].
Traditional flu shots typically rely on chicken eggs or cell-based cultures to grow the virus. mRNA technology instead provides the body with genetic instructions to produce a protein that triggers an immune response. This process can potentially allow for faster updates to the vaccine formula as flu strains evolve each year [3].
“The FDA granted full approval for adults aged 50 to 64, and accelerated approval for those aged 65 and older.”
The approval of mFLU-SIVA validates the mRNA platform's versatility for seasonal pathogens. While the relative efficacy of 26.6% is a specific data point for regulators to weigh, the shift toward genetic-based vaccines could reduce the manufacturing lead time required for annual flu shots, potentially allowing health officials to better match vaccines to the circulating strains of a given year.
