On March 13, 2025, the FDA announced influenza vaccine virus strain recommendations to vaccine manufacturers for the 2025-2026 influenza season in the United States.¹

In a press release, the federal agency stated it convened a meeting of members from the FDA, CDC, and Department of Defense (DoD) for an in-depth discussion that informed the selected compositions of the influenza vaccines to be used.

The FDA stated it does not foresee any impact of timing or availability of the vaccines for the American public for next flu season.

There were concerns among health care professionals that delays in vaccine availability could arise following the postponement of the CDC's Advisory Committee on Immunization Practices (ACIP) meeting, originally scheduled for February 26, 2025.^2,3

Shortly after the ACIP meeting was postponed, the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC), scheduled for March 13, 2025, was canceled.²

According to Tina Tan, MD, FIDSA, FPIDS, FAAP, editor in chief, Contemporary Pediatrics; president, Infectious Diseases Society of America (IDSA), these meetings typically contribute to the FDA's selection of influenza vaccine compositions. This year, however, compositions were selected and announced by the FDA without these meetings having occurred.

According to a report from Reuters published on March 20, 2025, the ACIP meeting has been rescheduled for April 15-16, 2025. The publication stated the reason for the initial postponement, according to the Department of Health and Human Services, was to accommodate public comment.⁵

"Basically what was in the document that [the FDA] released about the selection was they just basically took the strains that the [World Health Organization] (WHO) had used, and were going to use those strains to make the vaccines," Tan said in the video above.

The FDA stated that it used global and United States surveillance data to determine the recommendation for the vaccine manufacturers. These topics included, according to a press release¹:

• "Data and information on flu virus strains that are circulating in the US and globally and the types that are causing disease;
• Data and information on mid-season vaccine effectiveness for the 2024-2025 vaccines; and
• Information on candidate vaccine virus strains for use in manufacturing flu vaccines for the upcoming flu season."

FDA recommendations:

The federal agency recommended that the trivalent formulation of egg-based influenza vaccines for the upcoming flu season contain:

• An A/Victoria/4897/2022 (H1N1)pdm09-like virus;
• An A/Croatia/10136RV/2023 (H3N2)-like virus; and
• A B/Austria/1359417/2021 (B/Victoria lineage)-like virus

The FDA recommended that the trivalent formulation of cell- or recombinant-based influenza vaccines contain:

• An A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
• An A/District of Columbia/27/2023 (H3N2)-like virus; and
• A B/Austria/1359417/2021 (B/Victoria lineage)-like virus

With the recommendations, the FDA also listed the names of the interagency meeting participants from the FDA, CDC, and DoD who collectively made the recommendation.

"For FDA and for CDC, I did not recognize any names on there, and the individuals [who] are considered [to be] absolute flu experts, were not anywhere on that list," Tan told Contemporary Pediatrics. "What I found very interesting was that there were several people from the Department of Defense that were on that committee to decide what strain should be included in the vaccine."

Tan, a former member of VRBPAC (2019-2023⁵), stated the selection process for the 2025-2026 influenza vaccine composition was not traditional.

"Having sat on VRBPAC, which is the FDA committee that basically reviews surveillance data from the WHO and the CDC to determine what strains are included in the vaccine, I can tell you that you don't just look at WHO's choices and say 'that's what's going to be included,'" said Tan.

"You have to review all the other scientific information. My concern is the fact that this administration has pulled us out of WHO. So, if this vaccine is not as effective as it could be because they didn't review any other surveillance data, I think this administration will say, 'see, that's why we pulled out of WHO, because you can't trust them, and the flu vaccine is not worth taking,' or 'It's ineffective.'"

"That's my worry," Tan said.

Even with the unique situation in which the FDA recommended the influenza vaccine compositions, Tan said vaccination is crucial for protection, especially among a pediatric population.

"We just went through one of the most severe influenza seasons that we've had in decades," she said. "Part of it was the fact that there were so many people that were not taking influenza vaccination. It's a wait and see, but we could see another severe season if we don't get people vaccinated."

"I still think that having someone vaccinated is better than not being vaccinated, and with the increasing amount of vaccine hesitancy that is occurring, I would just ask all the providers to please take the time and talk to their patients about why it's so important to be vaccinated," added Tan. "Especially for infants and kids, because they can't advocate for themselves."

References:

1. Influenza Vaccine Composition for the 2025-2026 U.S. Influenza Season. FDA. Press release. March 13, 2025. Accessed March 24, 2025. https://www.fda.gov/vaccines-blood-biologics/influenza-vaccine-composition-2025-2026-us-influenza-season#:~:text=The%20FDA%20recommends%20that%20the%20trivalent%20formulation%20of%20cell%2D%20or,H3N2)%2Dlike%20virus%3B%20and

2. Fitch, J. How canceled government agency meetings could impact vaccination schedules, with Mary Koslap-Petraco, DNP. Contemporary Pediatrics. March 11, 2025. Accessed March 24, 2025. https://www.contemporarypediatrics.com/view/how-canceled-government-agency-meetings-could-impact-vaccination-schedules-with-mary-koslap-petraco-dnp

3. Fitch, J. Tina Tan, MD, on ACIP meeting postponement, public vaccine information reports. Contemporary Pediatrics. February 26, 2025. Accessed March 24, 2025. https://www.contemporarypediatrics.com/view/tina-tan-md-on-acip-meeting-postponement-public-vaccine-information-reports

4. Tirrell M. FDA meeting to choose flu vaccine composition canceled without explanation. CNN. February 27, 2025. Accessed March 24, 2025. https://www.cnn.com/2025/02/26/health/news-fda-meeting-to-choose-flu-vaccine-composition-canceled-without-explanation/index.html

5. US vaccine advisory meeting rescheduled for April. Reuters. March 20, 2025. Accessed March 24, 2025.