Moderna $MRNA published Phase 3 trial results Wednesday showing its mRNA flu vaccine, mRNA-1010, outperformed a standard-dose flu shot in adults aged 50 and older, with an FDA decision on the vaccine expected by Aug. 5.
The results appeared in the New England Journal of Medicine. Spanning 301 sites in 11 countries and funded by Moderna, the trial randomly assigned more than 40,000 participants ages 50 and up to receive either the mRNA vaccine or one of four standard-dose flu shots over the course of the 2024–2025 flu season, according to NBC News. About 2% of participants in the mRNA group became ill, compared with 2.8% in the standard shot group.
The vaccine achieved a relative vaccine efficacy of 26.6% against influenza illness in the overall study population, the company said. Efficacy was consistent across flu strains: 29.6% against A/H1N1, 22.2% against A/H3N2, and 29.1% against B/Victoria lineages. In adults aged 65 and older, relative efficacy was 27.4%.
People who received the mRNA vaccine reported more reactions like arm soreness, headache, and fatigue. According to NBC News, these side effects were usually mild and went away quickly.
"The publication of these peer-reviewed positive results in the New England Journal of Medicine reflects the strength of the clinical evidence supporting our ongoing regulatory submissions," Moderna CEO Stéphane Bancel said in a statement.
Earlier this year, the FDA turned down Moderna's initial submission on the grounds that the trial had measured mRNA-1010's performance against a standard-dose shot rather than the higher-dose formulation typically recommended for adults 65 and older — a choice regulators said may have inflated the apparent advantage of the mRNA product, according to NBC News. After public criticism of the initial rejection, regulators offered Moderna a path forward by restructuring the submission into two age-based tracks: one seeking conventional approval for the 50-to-64 cohort and another pursuing accelerated approval for people 65 and older, with the condition that a confirmatory trial be conducted post-approval.
An mRNA flu vaccine has yet to receive approval from any regulatory body worldwide, according to NBC News. Moderna has filed for authorization in several major markets — including the U.S., Europe, Canada, and Australia — and is aiming for its first approvals as early as 2026.
The political environment surrounding the review is complicated by HHS Secretary Robert F. Kennedy Jr., a longtime critic of mRNA technology who oversaw the cancellation of roughly $500 million in mRNA vaccine research funding last August, according to NBC News.
Moderna stock was up 2.80% on Wednesday morning.