The U.S. Food and Drug Administration has approved Moderna’s mFlusiva, the first influenza vaccine using mRNA technology to receive authorization in the United States.
The FDA approved the vaccine for two adult age groups: people aged 50 to 65 and those aged 65 and older. The approval requires Moderna to conduct an additional clinical trial among older adults, according to the company.
In a late-stage clinical trial, mFlusiva demonstrated approximately 27% greater effectiveness than a traditional flu vaccine.
mRNA technology could improve flu vaccine development
Scientists and public health experts have highlighted the potential benefits of mRNA-based flu vaccines, which use the same messenger RNA platform behind Moderna and Pfizer’s COVID-19 vaccines.
One major advantage of mRNA technology is the ability to manufacture vaccines more quickly, allowing researchers to better match vaccines with circulating influenza strains.
Moderna said its mRNA flu vaccine can move from strain selection to distribution within two to three months, compared with roughly six months for conventional flu vaccines.
“If you’re choosing the strain half a year before, how good can we be at sharpshooting?” said Dr. Ofer Levy, director of the Precision Vaccines Program at Boston Children’s Hospital.
Influenza causes hundreds of thousands of hospitalizations every year in the United States and contributes to tens of thousands of deaths. Young children and older adults remain among the groups most vulnerable to severe illness.
Traditional flu vaccines typically show effectiveness between 22% and 56%, according to the Mayo Clinic. Levy said higher effectiveness remains an important goal for future vaccines.
Approval came after regulatory debate
Although mFlusiva showed stronger performance than traditional flu vaccines in late-stage trials, its approval process faced uncertainty.
The approval came amid broader debate over mRNA technology. U.S. Health and Human Services Secretary Robert F. Kennedy Jr. has previously criticized mRNA vaccines, while the agency said the vaccine would enter the market with extensive post-market monitoring requirements, particularly for adults aged 65 and older.
The FDA initially declined to review Moderna’s application earlier this year before reversing that decision one week later. Regulators requested additional information because Moderna’s trial compared the vaccine with a standard flu shot among adults 65 and older, while the Centers for Disease Control and Prevention recommends high-dose flu vaccines for that age group.
Moderna said the FDA had previously approved the trial design. In June, an independent FDA vaccine advisory committee unanimously recommended approval of the vaccine.
Clinical trial showed promising results
The FDA decision was based on a late-stage clinical trial involving more than 40,000 older adults across 11 countries, including the United States.
Participants receiving mFlusiva reported side effects such as injection-site pain, fatigue and headaches more frequently than those receiving traditional vaccines. However, researchers described the reactions as mild to moderate.
Moderna plans to continue studying the vaccine in additional age groups, following the typical approach of initially targeting populations at higher risk of severe illness.
Availability and insurance concerns remain
Moderna said mFlusiva will be available for the upcoming flu season.
However, vaccines in the U.S. are typically formally recommended by the CDC’s Advisory Committee on Immunization Practices (ACIP) before widespread use. A federal court order has prevented the committee from meeting, creating uncertainty around official recommendations.
Dr. Levy said mFlusiva could legally be prescribed without ACIP approval, but access could be limited because many private insurers generally cover only vaccines recommended by the committee.
He also warned that federal programs such as Vaccines for Children and Medicaid rely on ACIP guidance, meaning the lack of an official recommendation could restrict distribution.
