The Food and Drug Administration approved the first mRNA flu vaccine on Wednesday, marking a significant advance in influenza prevention technology. Manufactured by Moderna and branded as mFLUSIVA, the vaccine uses messenger RNA technology, which instructs the body to produce a fragment of the virus to stimulate an immune response. This approach, previously used in COVID-19 vaccines, is expected to accelerate the development and adaptability of flu vaccines.
The approval authorizes mFLUSIVA for adults aged 50 to 64, with an accelerated approval granted for those 65 and older, allowing broad use while Moderna completes additional studies required for full approval. The company anticipates the vaccine will be available for the 2026-27 respiratory virus season.
Influenza remains a significant global health threat, causing more than 300,000 deaths annually worldwide. The 2024-25 flu season was particularly severe in the United States, with approximately 45,000 deaths reported, including at least 297 among children, according to the Centers for Disease Control and Prevention.
Moderna's vaccine demonstrated a relative efficacy of about 27% in a trial involving nearly 41,000 participants aged 50 to 64. In the study, 411 recipients of the mRNA vaccine contracted the flu compared to 557 participants who received a traditional flu shot, developed using older vaccine production methods involving fertilized chicken eggs. However, recipients of the mRNA vaccine reported a higher incidence of side effects such as injection-site pain, fatigue, and headaches, occurring at roughly twice the rate seen with the comparator vaccine. Serious adverse events potentially related to the vaccine included fainting, low blood pressure requiring hospitalization, and a case of perimyocarditis.
The approval followed initial resistance from the FDA, which earlier this year refused to review Moderna’s application—a rare move directed by Dr. Vinay Prasad, then head of the agency’s vaccine division and a noted critic of pharmaceutical companies and vaccine approvals. Prasad criticized the trial's choice of comparator vaccine, arguing it was not the best available option and could have biased results in Moderna's favor. Following public backlash, FDA commissioner Dr. Marty Makary reversed the decision, and the agency began reviewing the application.
The vaccine's authorization comes amid ongoing debates over mRNA technology and its role in public health. Health Secretary Robert F. Kennedy Jr., known for his opposition to some mRNA vaccine efforts, previously canceled multiple government-funded mRNA vaccine projects. Despite this, Moderna and many public health experts emphasize the potential of mRNA platforms to revolutionize responses to infectious diseases by enabling faster updates to vaccines as virus strains evolve.
Experts highlight that traditional flu vaccines require months to produce through older methods and often rely on growing viruses in eggs, which can be limiting. Moderna’s mRNA vaccine offers a more rapid production timeline and flexibility, potentially allowing countries to tailor vaccines more precisely to circulating strains each season.
“Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America’s seniors,” said Stéphane Bancel, Moderna’s chief executive. Dr. Georges C. Benjamin, executive director of the American Public Health Association, noted the vaccine’s benefits in potentially allowing rapid responses to emerging flu variants, describing it as a meaningful advancement over “archaic” traditional methods.