#2-80E. Assessing the Next Generation of Flu Protection: Modified mRNA Influenza Vaccine Data (NEJM, 2025)

Influenza remains a substantial public health burden despite licensed vaccines, often due to suboptimal effectiveness and challenges in rapid manufacturing; can the nucleoside-modified mRNA (modRNA) platform overcome these limitations and offer a superior solution? This Phase 3 trial randomized over 18,000 healthy adults aged 18 to 64 years to receive either a quadrivalent modRNA influenza vaccine or a licensed inactivated control vaccine, assessing relative efficacy, immunogenicity, and safety during the 2022–2023 season. The most significant finding is that the modRNA vaccine demonstrated a statistically superior relative efficacy of 34.5% compared to the licensed control vaccine against laboratory-confirmed influenza, fulfilling both noninferiority and superiority criteria. While the modRNA vaccine showed enhanced immune responses against Influenza A strains, it was associated with increased, though mostly mild-to-moderate, local and systemic reactogenicity events, including fever. Clinicians must note that interpretation requires caution because the primary endpoint was relative efficacy against a licensed comparator, not absolute efficacy against a placebo, necessitating an extrapolation of the benefit5. This study is crucial because the modRNA platform offers advantages like faster manufacturing and better strain matching, suggesting a potential paradigm shift toward improving seasonal influenza prevention and overall vaccine effectiveness in routine clinical practice.

Citation: D. Fitz‑Patrick, D.S. McVinnie, L.A. Jackson, et al. Efficacy, Immunogenicity, and Safety of Modified mRNA Influenza Vaccine. N Engl J Med. 2025. DOI: 10.1056/NEJMoa2416779

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