FDA Panel Unanimously Recommends Moderna's mRNA Flu Vaccine for Adults 50+

"All nine committee members voted in favor of recommending the vaccine for adults aged 50 and older."

The U.S. Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously on Thursday to recommend Moderna's mRNA influenza vaccine, mFlusiva, for adults aged 50 and older. This recommendation follows a period of regulatory uncertainty after the FDA initially declined to review Moderna's application.

Background

FDA Review Process

In February, the FDA issued a "refuse to file" letter to Moderna regarding its application for the mRNA flu vaccine. The agency's stated reason was that Moderna had not included a comparison to a high-dose flu vaccine for participants over 65 years old in its primary clinical trials. The FDA later reversed this decision and agreed to review the application following amendments from Moderna, including an agreement to conduct a confirmatory study in older adults using a high-dose flu shot after potential market authorization.

The FDA's initial refusal was attributed to Vinay Prasad, director of the FDA's Center for Biologics Evaluation and Research (CBER). Sources familiar with the matter stated that the decision came from Prasad rather than senior career staff, who had reportedly supported allowing the review to proceed. An anonymous senior FDA official described Moderna's clinical trial as a "brazen failure."

Moderna's Position

Moderna stated that the FDA had provided frequent input throughout their process and had not objected to the study design until the initial refusal. A Moderna spokesperson noted that the company had included data from a separate trial comparing its mRNA shot to a high-dose flu vaccine in its original submission. Moderna reported that CBER had communicated in April 2024 that while using a standard dose influenza vaccine in the control group would be "acceptable," they "recommend you use a vaccine preferentially recommended for use in older adults."

Andrew Nixon, a spokesperson for the Department of Health and Human Services (HHS), stated that Moderna "refused to follow very clear FDA guidance" regarding testing against the higher dose and "exposed participants age 65 and over to increased risk of severe illness."

mRNA Technology

Messenger RNA (mRNA) vaccines provide instructions for the body to produce flu antigens, stimulating immunity. Moderna's mRNA flu vaccine contains microscopic doses of mRNA for three to four flu strains. The technology was previously used in COVID-19 vaccines.

"Over 6 billion doses of mRNA vaccines have been administered globally since 2020."

Efficacy and Safety

Moderna's phase 3 trial involved over 40,000 subjects aged 50 and older across eleven countries, comparing Moderna's shot against an existing standard-dose vaccine. Researchers at Washington University in St. Louis analyzed the immune response in 75 patients and found that the mRNA vaccine produced a longer-lasting response and antibodies recognizing more flu strains compared to traditional vaccines. Moderna also submitted data indicating their shot generated more antibodies than the higher-dose alternative for seniors.

Dr. Gauri Raval, medical officer of the FDA's Division of Clinical and Toxicology Review, stated that the Moderna mRNA flu vaccine may offer greater efficacy than standard-dose comparators in preventing more severe influenza-associated illness. The FDA found no major safety issues or deficiencies.

Dr. Anna Durbin, director of the Center for Immunization Research at Johns Hopkins University and VRBPAC member, stated that the vaccine underwent full efficacy evaluation per standard FDA guidance, including phase 3 studies in tens of thousands of individuals. Dr. Jesse Goodman, former director of FDA's Center for Biologics Evaluation and Research, noted that there is no risk of DNA integration with mRNA vaccines.

Meeting Highlights

CDC Presentation

Dr. Lisa Grohskopf from the CDC presented data showing at least 32 million flu cases, 390,000 hospitalizations, and 24,000 deaths in the U.S. during the 2025-2026 flu season. She stated that approximately 85% of those eligible for vaccination were not fully vaccinated.

Moderna Presentation

Dr. Evan Anderson, vice president of epidemiology at Moderna, highlighted the issue of strain mismatch with current vaccines. He said the proposed mRNA vaccine could reduce the time to develop a strain-specific vaccine from about six months to two to three months, potentially improving accuracy and efficacy.

Committee Vote

After six and a half hours, all nine committee members voted in favor of recommending the vaccine for adults aged 50 and older.

Regulatory and Policy Context

Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia and former VRBPAC member, characterized the FDA's initial refusal to review the application as unusual. Offit expressed relief that VRBPAC remained largely intact, in contrast to the CDC's Advisory Committee on Immunization Practices (ACIP), which was reorganized. Dr. Durbin noted that ACIP, which determines vaccine usage recommendations, has not held its usual spring flu meeting in 2025.

Secretary Kennedy could reconvene the ACIP committee at any time, subject to its charter. If approved and recommended, Moderna stated the vaccine could be available for the next flu season.

Expert Perspectives

Some external experts voiced concerns regarding the FDA's decision-making and communication practices. Richard Hughes IV, a law professor, suggested the FDA's stated reasons might be "pretext and obfuscation," attributing the rejection to a "predetermined anti-vaccine agenda." Dorit Reiss, a law professor, criticized the anonymity of the FDA official, suggesting it implies an unwillingness to defend a potentially "weak, flawed and untenable" decision. Angela Rasmussen, a virologist, suggested that the FDA might be "coming up with reasons to not approve mRNA anything."

"Such actions could harm the industry's ability to make investments if FDA communications are not honored."

Several experts expressed concerns that such regulatory uncertainty could deter pharmaceutical companies from investing in and developing new vaccines. Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy, stated that the FDA appeared to have reversed its established process. Ian Spatz, founder and CEO of the Rock Creek Policy Group, noted that such actions could harm the industry's ability to make investments if FDA communications are not honored. Joshua Sharfstein, a former FDA principal deputy director, likened the situation to overturning a call without new evidence and a compelling explanation.

Nixon dismissed concerns that mRNA and other vaccines are being targeted by officials as "baseless."