The US Food and Drug Administration granted traditional approval for Moderna's mRNA flu vaccine, mFlusiva, for adults aged 50 to 64 and accelerated approval for those 65 and older on August 5, 2026 [1, 2, 3, 4]. The approval follows a unanimous vote from an FDA advisory committee in June 2026 supporting the vaccine's use in this age group [1, 2, 4].
Moderna's approval came after late-stage Phase 3 trials that enrolled approximately 40,000 to 41,000 adults 50 years and older. The trials showed mFlusiva was about 26.6% more effective in preventing flu illness compared to a licensed standard-dose flu vaccine [1, 2, 3]. The vaccine conveys protection by using messenger RNA technology similar to Moderna's COVID-19 shot, which instructs cells to produce influenza antigens and trigger immune responses, contrasting with traditional egg-based flu vaccines [1, 5, 6, 3].
The FDA initially refused in February 2026 to review Moderna's application, citing Moderna's use of a standard-dose comparator vaccine rather than the FDA-preferred high-dose vaccine recommended for older adults as a concern [1, 2, 5, 6, 3]. Less than a week later it reversed that decision, allowing a full review and leading to approval in August [1, 4, 2, 5, 6, 3]. The early refusal took place amid controversy involving FDA leadership under Robert F. Kennedy Jr., who challenged mRNA vaccine technology and cut funding for mRNA research, including an estimated $500 million in US government support [1, 2, 5, 6].
Moderna must conduct a post-marketing study to provide additional evidence of mFlusiva's benefit specifically in adults aged 65 and older to confirm its effectiveness in that group [1, 4, 2]. Most reported side effects from the trial were mild to moderate and temporary, primarily injection site pain, fatigue, headache, and muscle pain, at a higher rate than traditional flu vaccines but consistent with typical vaccine responses [3].
Despite approval, Moderna's commercial sales of mFlusiva are not expected to be significant until the 2027-2028 flu season due to missed contracting cycles and typical vaccine purchasing timelines [1, 5, 6]. However, the vaccine is expected to be available in select US retailers in the coming weeks ahead of the 2026-2027 flu season [4, 2].
mFlusiva will compete with flu vaccines from Sanofi, GSK, CSL Seqirus, and AstraZeneca in the US market [1]. Meanwhile, the US Centers for Disease Control and Prevention's vaccine advisory panel remains involved in legal challenges that could affect official recommendations and insurance coverage, possibly limiting recommendations to immunocompromised or high-risk groups [5, 6].
Moderna CEO Stéphane Bancel said, "Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America's seniors. This approval also reflects the ongoing potential of our mRNA platform." Law professor Richard Hughes IV criticized the FDA's initial refusal, calling it "pretext and obfuscation when the real agenda is rejecting conventional science and serving a predetermined anti-vaccine agenda" [2, 3].
Moderna previously withdrew its US application for a combination COVID-19-flu mRNA vaccine in May 2025 after the FDA requested more data on the flu component. That combo vaccine later gained approval in Europe in February 2026 [1, 4, 2].
The earliest market availability of mFlusiva is expected this month in select US retailers ahead of the upcoming flu season, while significant commercial impact is projected starting with the 2027-2028 season [4, 2, 1, 5, 6].
