The U.S. Food and Drug Administration approved mFlusiva, an mRNA-based influenza vaccine developed by Moderna, on August 5 for people ages 50 and older. The decision follows a study of more than 40,000 participants in that age group published in the New England Journal of Medicine in May 2026. Participants who received a single dose of mFlusiva were on average 27% less likely to develop lab-confirmed influenza-like illness than those who received one of four currently available flu vaccines.
The mRNA platform allows manufacturers to update the vaccine in roughly six weeks by swapping genetic sequences, compared with up to six months for traditional egg-based production. This shorter timeline could improve the match between vaccine strains and circulating viruses, a persistent challenge that has caused seasonal efficacy to swing between 20% and 60%. Dr. Jeanne Marrazzo, CEO of the Infectious Diseases Society of America, described the approval as a historic scientific and public-health milestone.
The FDA initially issued a Refusal-to-File letter in February, stating the trial lacked a proper control arm and should have compared mFlusiva to high-dose vaccines for people 65 and older. After meetings between Moderna and the agency, the FDA reversed course and granted full approval for ages 50 to 64 and accelerated approval for those 65 and older, contingent on a further study in the older group. Marrazzo said she could not recall a similar about-face and suggested political influence may have played a role.
The approval arrives as federal vaccination policy has shifted. In January, the Trump administration revised guidance to leave flu vaccination decisions to individuals and their physicians, departing from prior CDC recommendations for annual shots for everyone six months and older. Major medical organizations, including the American Academy of Pediatrics and the American Medical Association, continue to endorse broader vaccination.
Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine skeptic, halted 22 mRNA vaccine projects worth $500 million in 2025. Marrazzo noted that public trust in vaccines and mRNA technology has eroded despite scientific advances, raising questions about uptake of the new shot. Moderna plans to make mFlusiva available this fall as flu vaccination campaigns begin.
The trial demonstrated a measurable efficacy advantage for mFlusiva over existing options in a high-risk population. However, real-world effectiveness and acceptance will depend on ongoing studies, evolving public-health guidance, and public confidence in mRNA vaccines.
FDA Approves the First mRNA Flu Vaccine
This is an independent summary. The complete reporting, supporting context and any primary documents remain with TIME.