The Food and Drug Administration (FDA) rejected Moderna’s request to have its mRNA (messenger ribonucleic acid)-based flu vaccine approved, the drugmaker said Tuesday.
The move is the latest sign that the FDA, under the direction of Health and Human Services Secretary Robert F. Kennedy Jr., is slowing approval of vaccines and taking a tougher stance on those that use mRNA technology.
Moderna’s vaccine uses the same mRNA technology as its COVID-19 vaccine.
In a statement issued Tuesday, Moderna said the FDA did not identify any safety or effectiveness issues with the vaccine. Instead, he noted that the FDA questioned the “comparator” used in its clinical trial, meaning the vaccine the company used as a reference to evaluate its own vaccine.
The FDA stated that using the standard flu vaccine as a comparator “does not reflect the best available standard of care.” The standard flu vaccine is approved by the FDA.
(The FDA seeks to ban a common additive in breads, ice creams, cereals and meats suspected of causing cancer)
However, Moderna stated that the reason given by the agency is “inconsistent” with what regulators had communicated to the company in 2024 and 2025.
“Shouldn’t be controversial conduct a thorough review of a flu vaccine application that uses an FDA-approved vaccine as a comparator in a study that was discussed and agreed upon with CBER before it began,” Moderna CEO Stéphane Bancel said in the statement, referring to the FDA’s Centers for Biologics Evaluation and Research, which review and approve vaccines as well as other treatments, such as gene therapies.
Moderna claimed last year that its mRNA flu vaccine was 26.6% more effective than the standard flu vaccine, according to a Phase III clinical trial.
In an emailed statement, Andrew Nixon, a spokesman for the Department of Health and Human Services, which oversees the FDA, said, “FDA generally does not comment on regulatory communications to individual sponsors.”
Last year, Kennedy ordered that all new vaccines be subject to placebo-controlled clinical trials.
(More than 700 cases of measles are reported in at least 20 US states in 2026 alone.)
When vaccines are already available for a disease, it is considered unethical to give a placebo to participants in clinical trials, rather than comparing the new vaccine with the existing one. Giving a placebo would leave people who would otherwise be protected vulnerable to infection.
Last May, Moderna withdrew its application for approval of its mRNA-based combination flu and COVID-19 vaccine after the FDA requested more data.
Kennedy, who is an anti-vaccine activist, has downplayed the benefits of vaccines and singled out vaccines made with mRNA as especially dangerous, calling the mRNA-based COVID-19 vaccine “the deadliest vaccine ever made.”
Numerous studies have shown that mRNA vaccines are safe and effective. A 2023 analysis published in JAMA Pediatrics reviewed 17 studies covering more than 10 million children ages 5 to 11 who received the Pfizer or Moderna COVID-19 vaccines. Vaccinated children had a lower risk of infection and hospitalization compared to those who were not vaccinated.
(Drinking coffee or tea daily would reduce the risk of dementia by up to 18%, according to a study)
In August, the Department of Health and Human Services canceled nearly $500 million in funding for mRNA vaccine research.
Several states have introduced bills to ban mRNA vaccines.
Regulators in the European Union, Canada and Australia have accepted Moderna’s application for the mRNA flu vaccine, the company said.
