Moderna has secured US Food and Drug Administration (FDA) approval for its mRNA influenza vaccine, overcoming initial data qualms from the agency and successfully navigating a wider US vaccine landscape notorious for hesitancy with the technology.
The approval means the vaccine, known as mFlusiva, becomes the first authorised for preventing flu in the US using mRNA technology. It is licensed for preventing seasonal influenza in all adults aged 50 years and older. This is split into traditional approval for adults aged 50 to 64, and accelerated approval for those aged 65 years and older.
Shares in Nasdaq-listed Moderna rose 1.77% to $58 at market open on 6 August following the news, compared to a pre-announcement market close of $56.99.
Approval in the 50 to 64 age group was based on results from a Phase III trial that enrolled more than 40,000 individuals. mFlusiva demonstrated superiority over standard-dose licensed vaccines in preventing influenza-induced illness.
For the older age group, a separate Phase III trial pitted mFlusiva against a high-dose comparator. As part of the accelerated approval, Moderna will conduct a postmarketing clinical trial to confirm clinical benefit in this population.
Comparison to a standard-dose in the former study was the main qualm of the FDA when it issued a rare refuse to file (RTF) letter in February 2026. As revealed soon after, the FDA’s Center for Biologics Evaluation (CBER) then-chief, Vinay Prasad, noted that the Phase III trial failed to use an optimal comparator.
News of the FDA declining to even look at the application generated shockwaves in the vaccine development space. At the time, Moderna’s stock slumped by more than 10%.
Reprieve arrived only a week after the RTF was published when the FDA accepted an amended application after meeting with Moderna. In June, the FDA’s Vaccines and Related Biological Products Advisory Committee voted unanimously that the benefits of Moderna’s jab outweighed its risks across both the 50-to-64-year age group and in patients ages 65 years and older.
The approval, which marks Moderna’s fourth FDA-approved vaccine, therefore caps off a far from straightforward regulatory journey. The company will also need to contend with uncertain mRNA optics in the US. Health secretary Robert F Kennedy Jr (RFK Jr) has long claimed that mRNA technology poses a higher risk profile than traditional vaccines, despite clinical evidence. Under his leadership, the Department of Health and Human Services (HHS) cancelled $500m worth of federally funded mRNA contracts in August 2025.
Nevertheless, analysts commented that the approval is good news for Moderna’s revenue guidance. William Blair analysts place a conservative $1.16bn peak sales forecast for mFlusiva. An advantage of mRNA vaccines is the ability to manufacture updated versions in response to new strains quicker than traditional protein-based vaccines.
Moderna will now require Centers for Disease Control and Prevention (CDC) recommendation for the jab to be used in national immunisation programmes in upcoming flu seasons, meaning all eyes will be on the next Advisory Committee on Immunization Practices (ACIP) meeting in mid-October.
The ACIP panel has also been embroiled in controversy under RFK Jr’s oversight. The health secretary has replaced members with individuals critical of vaccines and government guidance during the Covid-19 pandemic. In December 2025, the panel controversially voted to revoke newborn hepatitis B vaccine recommendations, which was met with dismay from medical bodies and charities.
