FDA approves Moderna's mFlusiva, the first mRNA-based seasonal flu vaccine, for adults 50 and older

Approval and trial data

The U.S. Food and Drug Administration approved Moderna's mFlusiva (also known as mRNA-1010) on August 5, 2026, the first messenger RNA-based vaccine for seasonal influenza. The shot received a traditional approval for adults aged 50 to 64 and an accelerated approval for those 65 and older, with Moderna required to run an additional postmarketing study to confirm benefit in the older group. The approval was based on a Phase 3 trial enrolling 40,805 adults across 11 countries, which showed the vaccine was 26.6% more effective than a licensed standard-dose flu vaccine. Separate late-stage data showed stronger antibody responses than Sanofi's high-dose flu vaccine in adults 65 and older. Moderna said the vaccine would be available "in a few weeks," in time for the 2026-2027 respiratory virus season.

Safety profile

Moderna's data showed no major safety issues, though the shot caused temporary reactions including injection-site pain, fever, headache, fatigue, tiredness, aches and myalgia at somewhat higher rates than existing flu vaccines. Most adverse reactions were described as mild to moderate and transient. The vaccine uses mRNA technology to prompt the body to produce influenza antigens, an approach that could allow faster updates to match circulating strains compared with conventional egg-based flu shots.

A turbulent review process

The path to approval was unusually contentious. In February 2026, Vinay Prasad, then head of the FDA's vaccine and biologics division and an ally of Health Secretary Robert F. Kennedy Jr., refused to even review Moderna's application, arguing the company had not compared its vaccine against the correct comparator. Career FDA scientists had previously signed off on the trial design. Moderna publicly pushed back, and the FDA reversed course within a week. Prasad was pushed out of the agency at the end of April 2026.

In June, a panel of independent FDA advisers voted unanimously to recommend approval, and the agency set August 5 as its decision deadline. The review spanned seven months in total.

Political context

Health Secretary Robert F. Kennedy Jr., a long-time vaccine critic, pulled $500 million in mRNA vaccine research funding last year and has called the mRNA COVID-19 vaccine the "deadliest vaccine ever made." The Trump administration also slashed funding for mRNA vaccine research and curtailed access to COVID vaccines. President Trump had embraced mRNA technology during his first term to produce COVID vaccines, but the backlash against pandemic responses led to the technology being vilified by some.

“The FDA approval of mFLUSIVA demonstrates the continued strength and versatility of our mRNA platform. Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America's seniors.”

Market outlook

More than 45,000 Americans died from influenza during the 2024-2025 season, with flu-related hospitalizations and outpatient visits reaching their highest levels in 15 years. mFlusiva will compete with flu vaccines from Sanofi, GSK, CSL Seqirus and AstraZeneca. Analysts do not expect meaningful revenue until the second half of 2027, as Moderna missed the contracting cycle for the 2026 U.S. flu season. Jefferies analysts forecast $750 million in U.S. sales of Moderna's flu shot and a combination COVID-flu vaccine by 2030. Moderna withdrew its application for the combo shot last year after the FDA sought additional evidence on the flu component's effectiveness.