The FDA has approved mFlusiva, Moderna's mRNA-based flu vaccine, marking the first time this technology is used for influenza protection in people 50 and older. The vaccine, which builds on the mRNA technology used in COVID-19 shots, is set to become available this fall and represents a significant shift in how flu vaccines are manufactured and matched to circulating strains.

How Does mRNA Flu Vaccine Technology Work Differently?

Traditional flu shots use weakened or inactivated virus pieces to train your immune system. mRNA vaccines work differently. Instead of containing virus material, they deliver genetic instructions that tell your body's cells to produce a viral protein, which then triggers an immune response. This approach offers a major advantage: mRNA vaccines can be manufactured much faster than traditional flu shots, which are grown in cells or chicken eggs.

The speed of manufacturing matters because flu strains change constantly. With traditional vaccines, scientists must select which virus strains to include around February, about six months before shots are given. With mRNA technology, that selection can happen in May, much closer to when people actually get vaccinated. This flexibility means the vaccine can be better matched to the strains most likely to circulate during the upcoming flu season.

"This affords us a lot more flexibility in trying to match up the right strain of virus circulating with what's in the vaccine," explained Dr. Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota.

Dr. Michael Osterholm, Director of the Center for Infectious Disease Research and Policy at the University of Minnesota

What Do the Study Results Show About Effectiveness and Safety?

Moderna's mFlusiva was found to be approximately 27% more effective than standard flu shots during the 2024-25 vaccine season, based on a study that enrolled over 40,000 people older than 50. The vaccine received two different types of approval: standard approval for adults 50 to 64 years old, and accelerated approval for adults 65 and older. The accelerated pathway came after the FDA initially rejected Moderna's application, citing concerns about how the vaccine was compared to existing options.

The vaccine did show higher rates of side effects compared to standard flu shots, but most were mild to moderate. Common reactions included injection site pain, muscle and joint pain, nausea, vomiting, fever, headache, and chills, and these typically resolved within days. Serious adverse events occurred at similar low rates in both the mRNA vaccine group and the standard vaccine group, and most serious events were assessed as unrelated to vaccination.

Who Should Consider Getting the mRNA Flu Vaccine?

The vaccine is approved for people 50 and older, but the approval process differed by age group. For adults 50 to 64, the vaccine received standard approval based on its superior antibody response. For adults 65 and older, the FDA granted accelerated approval with a condition: Moderna must conduct additional studies during the upcoming flu season to confirm that better antibody production actually translates to better real-world protection against illness.

People should not receive mFlusiva if they have an allergy to any of its ingredients or if they have previously experienced Guillain-Barré syndrome after flu vaccination.

Steps to Take Before Getting the mRNA Flu Vaccine

• Review Your Age and Eligibility: The vaccine is approved for adults 50 and older. If you fall into this age group and have no history of severe allergic reactions to vaccine ingredients or Guillain-Barré syndrome, you may be a candidate.
• Discuss Your Health History with Your Doctor: Talk to your healthcare provider about whether mFlusiva is appropriate for you, especially if you have chronic health conditions or take multiple medications that could interact with the vaccine.
• Understand the Side Effect Profile: Know that you may experience mild to moderate reactions like arm soreness, muscle aches, or low-grade fever for a few days after vaccination, which is normal and typically resolves quickly.
• Plan Your Vaccination Timing: The vaccine is expected to be available this fall, but availability may be limited at first since many pharmacies and clinics order flu vaccines earlier in the year.

What Happens Next With CDC Recommendations?

Normally, after a new vaccine is approved, the CDC's Advisory Committee on Immunization Practices reviews the data and issues recommendations about whether doctors should offer it. However, that committee has not met since March 2026, when a federal judge ruled that Health and Human Services Secretary Robert F. Kennedy Jr. did not follow proper legal procedures when he replaced all committee members. A meeting is currently scheduled for October.

"The Food and Drug Administration's approval of a new mRNA flu vaccine is welcome news and provides another important option to help protect people from a virus that sends hundreds of thousands of Americans to the hospital each year and claims thousands of lives," stated Dr. Ronald G. Nahass, president of the Infectious Diseases Society of America.

Dr. Ronald G. Nahass, President of the Infectious Diseases Society of America

Experts emphasized that the additional study Moderna will conduct this fall in adults 65 and older is important. The company will compare mFlusiva's clinical benefit against the enhanced-dose flu vaccines already recommended for older people, which are designed to provide stronger protection in this vulnerable population.

Because most pharmacies and clinics order their flu vaccines earlier in the year, mFlusiva's availability may be somewhat limited during the 2026-27 flu season. However, the approval represents a major step forward in flu vaccine technology and offers older adults a potentially more effective option as the flu season approaches.