FDA Approves Moderna's mFLUSIVA, the World's First mRNA-Based Seasonal Flu Vaccine
On August 5, 2026, the U.S. Food and Drug Administration (FDA) approved Moderna’s mFLUSIVA (mRNA-1010), marking a historic milestone as the first-ever messenger RNA-based vaccine cleared for seasonal influenza1. The vaccine is indicated for all adults aged 50 and older, arriving in time for the upcoming 2026–2027 respiratory virus season.
The regulatory milestone represents a significant validation of Moderna's mRNA technology outside of COVID-19. The FDA granted standard approval for adults aged 50 to 64 and accelerated approval for seniors aged 65 and older. To support the accelerated approval in the older cohort, Moderna has agreed to conduct a massive postmarketing confirmatory trial enrolling up to 800,000 participants to compare mFLUSIVA against an enhanced standard-of-care vaccine (such as a high-dose or recombinant flu vaccine).
Efficacy and Safety Profile
The approval is backed by data from a robust Phase 3 clinical program involving more than 40,000 adults aged 50 and older. In clinical trials, mFLUSIVA demonstrated a 26.6% relative vaccine efficacy (RVE) improvement over a licensed standard-dose flu vaccine in the younger cohort, and up to a 47.9% RVE against high-acuity outcomes. The safety and reactogenicity profile remained consistent with established mRNA class effects, showing mostly mild-to-moderate, transient local and systemic reactions.
Overcoming a "Refusal to File" Standoff
The approval caps a dramatic regulatory turnaround. Earlier in 2026, the FDA—then led by Commissioner Marty Makary and Deputy Commissioner Vinay Prasad—initially issued a "refusal-to-file" (RTF) letter for the vaccine's application. The agency had raised concerns about Moderna's use of a standard-dose flu vaccine as the comparator arm in its Phase 3 trials, arguing it did not reflect the "best-available standard of care." Following public backlash and a formal Type A meeting, the FDA reversed its decision and agreed to review the application.2 In June 2026, the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously (9–0) in favor of the vaccine's benefit-risk profile, setting the stage for the final approval.
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An instance of mRNA technology must transition from emergency pandemic response to seasonal and proactive clinical footholds. — The approval validates mRNA's move out of emergency pandemic response and into the highly competitive seasonal respiratory market. ↩︎
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An instance of Leadership churn at regulatory agencies triggers a systemic softening of clinical standards. — The new regulatory administration backed down on its initial refusal-to-file decision, signaling a more accommodating stance toward vaccine developers. ↩︎