What Were the Clinical and Regulatory Findings That Supported Approval?
The FDA's approval for adults 50 through 64 years is based on a Phase 3 randomized, observer-blind, active-controlled trial (NCT06602024) enrolling 40,805 adults across 11 countries. The primary endpoints were safety and relative vaccine efficacy against reverse transcription polymerase chain reaction-confirmed influenza-like illness caused by any influenza A or B strain, benchmarked against a licensed standard-dose comparator.
mFLUSIVA demonstrated a relative vaccine efficacy of 26.6% (95% CI: 16.7%, 35.4%) versus standard-dose, meeting the study's pre-specified superiority criterion.1 In the 65-and-older subgroup, relative vaccine efficacy reached 27.4%. Solicited adverse reactions of injection site pain, fatigue, headache and myalgia were predominantly mild to moderate and resolved within one to two days, with no new safety signals identified.
Approval for adults 65 and older was granted under the FDA's accelerated approval pathway, based on immunogenicity data from a separate trial (NCT05827978) enrolling 2,992 adults comparing mFLUSIVA against a high-dose inactivated influenza vaccine.2 A confirmatory postmarketing trial is required to verify clinical benefit in that population, which is an important regulatory obligation given that adults 65 and older represent the highest-burden demographic for influenza-related hospitalization and death.3
What Does mFLUSIVA's Approval Signal for the Future of mRNA-Based Biologics?
From a platform perspective, each new mRNA-based approval adds to a body of regulatory precedent for lipid nanoparticle delivery, manufacturing process validation, and clinical development methodology that can inform subsequent programs in infectious disease, oncology, rare disease, and beyond.
Regulatory submissions for mFLUSIVA have been accepted for review in the European Union, Canada and Australia, with additional country submissions planned during 2026. The global rollout will test the scalability of Moderna's manufacturing network and cold chain infrastructure across regulatory jurisdictions with varying requirements for process comparability and technology transfer.
The FDA Vaccines and Related Biological Products Advisory Committee unanimously recommended mFLUSIVA for adults 50 and older prior to approval, affirming the benefit-risk assessment that has underpinned prior mRNA vaccine reviews.4 For biopharmaceutical developers watching this space, the precedent suggests regulators are increasingly comfortable with mRNA construct updates and formulation data packages as a basis for strain or target changes. This represents a potentially significant regulatory efficiency for future iterations of platform-derived vaccines.
Limitations to monitor include the accelerated approval status in adults 65 and older, reactogenicity rates that were modestly higher than conventional comparators, and the operational demands of lipid nanoparticle cold chain management at population-level distribution volumes.
Sources
1. mRNA-1010, an mRNA-Based Influenza Vaccine, is Safe and Efficacious in Adults Aged ≥50 Years. Open Forum Infect Dis. 2025.
2. A phase 3 randomized safety and immunogenicity trial of mRNA-1010 seasonal influenza vaccine in adults. Vaccine. 2025.
3. Mertz D, et al. High Clinical Burden of Influenza Disease in Adults Aged ≥ 65 Years: Can We Do Better? A Systematic Literature Review. Vaccines (Basel). 2023;11(2):439.
4. FDA Advisory Committee Supports Moderna mRNA Flu Vaccine Review. AJMC. 2026.