Moderna has presented encouraging clinical data for two investigational influenza vaccine candidates at IDWeek 2025 in Atlanta, demonstrating both efficacy advantages over standard vaccines and strong safety profiles that could advance the company's mRNA platform into seasonal and pandemic flu prevention.
Seasonal Flu Vaccine Shows Superior Efficacy
The company's seasonal influenza vaccine candidate mRNA-1010 achieved a relative vaccine efficacy (rVE) of 26.6% (95% CI: 16.7%, 35.4%) compared to a licensed standard-dose influenza vaccine in the overall study population of adults aged 50 and above. The results met prespecified superiority criteria and showed consistent efficacy across vaccine-included strains, including Influenza B strains.
More notably, mRNA-1010 demonstrated enhanced protection against severe disease outcomes, with an rVE of 33.7% (95% CI: 12.0, 50.0%) for preventing medically-attended influenza compared to standard vaccination. This finding suggests the mRNA-based approach may offer particular benefits in reducing healthcare utilization and more serious flu complications.
H5N1 Pandemic Preparedness Shows Strong Immunogenicity
Moderna's pandemic influenza candidate mRNA-1018, designed to target H5N1, demonstrated robust immunogenicity in a Phase 1/2 dose-ranging study involving healthy adults 18 years and older. The vaccine showed rapid immune response development, with 79.5% (95% CI: 74.3, 84.1) of participants achieving protective immune responses as early as three weeks after the first dose.
Three weeks following the second dose, 97.8% of participants (95% CI: 95.4, 99.2) achieved immune responses at or above levels considered protective from influenza. The durability of the immune response proved particularly encouraging, with 70.6% (95% CI: 64.8, 76.0) of participants maintaining seroprotective titers six months after the second dose.
Safety Profile Supports Clinical Development
Both vaccine candidates demonstrated favorable safety profiles with no safety concerns identified across all dose levels tested. For mRNA-1010, injection site pain was the most common local solicited adverse reaction, while fatigue, headache, and myalgia were the most frequently reported systemic adverse reactions. The mRNA-1018 candidate was similarly well-tolerated across all dose levels in the study.
Clinical Implications for mRNA Vaccine Platform
The data presented at IDWeek 2025 represents continued validation of Moderna's mRNA vaccine technology beyond COVID-19 applications. The superior efficacy demonstrated by mRNA-1010 against standard influenza vaccines, particularly for severe outcomes, suggests potential advantages of the mRNA platform in addressing seasonal flu prevention challenges.
The strong immunogenicity and durability shown by mRNA-1018 against H5N1 could prove crucial for pandemic preparedness efforts, especially given ongoing concerns about avian influenza transmission risks. The ability to achieve protective responses in nearly 98% of participants within three weeks of completing vaccination could enable rapid population protection in a pandemic scenario.
The presentations were delivered by Eleanor Wilson, MD, MHS for the mRNA-1010 data and Brett Leav, MD for the mRNA-1018 results during oral sessions on October 20, 2025, as part of Moderna's broader portfolio of vaccine candidates being presented at the conference.
