The Food and Drug Administration should approve the first messenger ribonucleic acid (mRNA) vaccine for influenza, the agency’s vaccine advisory panel said on June 18.
The Vaccines and Related Biological Products Advisory Committee in a unanimous vote advised the FDA to approve an mRNA flu shot from Moderna for adults aged 50 and older.
“The presented data do indicate efficacy against flu with no safety signals,” Dr. Hana El Sahly, a professor at the Baylor College of Medicine and committee member who worked on a trial for Moderna’s COVID-19 vaccine, said after the vote.
“I think that this particular platform adds exciting ways that we can actually move our vaccines to the future,” Dr. Hayley Gans, a Stanford Medicine Children’s Health pediatrics professor and fellow committee member, added.
The FDA typically accepts the committee’s advice.
Advisers said that data from several clinical trials, including one that featured 40,000 participants, were sufficient to approve the vaccine.
The vaccine was 26.6 percent more effective in preventing influenza in that trial than a standard, already available flu shot. Compared to 2.8 percent of the participants who received the standard vaccine, 2.0 percent of the Moderna recipients experienced influenza-like illness in the trial. Adverse reactions were higher among Moderna vaccine recipients.
FDA officials who are no longer with the agency previously took issue with that trial because it did not use a high-dose comparator vaccine, which the Centers for Disease Control and Prevention currently recommends for older individuals.
Moderna executives said on Thursday that the standard comparator was chosen for multiple reasons, including that they have historically served as a benchmark for testing new flu vaccines. They also said that a separate study that used the high-dose vaccine and looked at immune responses among the elderly provided additional support for clearing the company’s shot.
Moderna’s vaccine would receive traditional approval for adults aged 50 to 64, if the FDA acts on the advice. Traditional approval requires “substantial evidence” of safety and efficacy.
Regulators would also grant for adults aged 65 and older accelerated approval, which requires evidence that a product that serves “an unmet medical need” is “reasonably likely to predict clinical benefit.” Accelerated approval would include a requirement for a post-approval trial. That trial is expected to enroll 400,000 people, Moderna executives said on Thursday.
The executives said that the varying levels of effectiveness of the currently available influenza vaccines highlight an unmet medical need. Those vaccines were estimated to be 11 percent to 46 percent effective among children, and 23 percent to 34 percent effective among adults, in late 2025 and early 2026, according to a CDC presentation. And historically, the effectiveness has been as low as 19 percent and as high as 60 percent.
Flu primarily circulates in the fall and winter. Officials in the spring try to predict which strain will be circulating in the following virus season, giving manufacturers about half a year to produce shots with updated formulations before vaccination begins in the early fall. That can result in a mismatch between targeted and circulating strains, an issue that the FDA and Moderna said the mRNA shot could address.
Downsides of the shot include higher rates of adverse events when compared to the already available vaccines.
Vaccines containing mRNA are cleared in the United States for COVID-19 and respiratory syncytial virus. There are currently nine approved influenza vaccines in the United States. None utilizes mRNA.