US Will Transition to Trivalent Flu Vaccines for 2024-2025

March 8, 2024 – On March 5, 2024, the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) met to discuss and make recommendations on the vaccine viruses for U.S. flu vaccines for the 2024-2025 flu season. The Committee recommended that all 2024-2025 U.S. flu vaccines be three-component (trivalent) vaccines and include an influenza A(H1N1), an A(H3N2) and a B/Victoria-lineage vaccine virus. Because influenza B/Yamagata viruses, which are included in current four-component (quadrivalent) flu vaccines, are no longer actively circulating, their inclusion in flu vaccines is no longer warranted.

Flu places a substantial health burden on the United States each year, sickening millions, hospitalizing hundreds of thousands and killing thousands to tens of thousands. Flu vaccines have been recommended in the United States for more than 50 years and have been shown to reduce the risk of flu and its potentially serious complications in people who get vaccinated. CDC recommends annual flu vaccination for everyone 6 months and older with rare exception.


The composition of U.S. flu vaccines is reviewed annually, and new flu vaccines are manufactured each year. From the 1958-1959 through 1977-1978 flu seasons, the number of vaccine viruses included in U.S. flu vaccines varied. From the 1978-1979 through 2012-2013 seasons, U.S. flu vaccines were trivalent. During those 35 seasons, flu vaccines included three vaccine viruses: an influenza A(H1N1), an A(H3N2), and a B-lineage vaccine virus (either from the B/Yamagata or B/Victoria lineage). Quadrivalent flu vaccines became available in the United States during the 2013-2014 flu season. These vaccines contained a fourth component—a second influenza B virus—in order to protect against both lineages of influenza B viruses. Quadrivalent flu vaccines were available in the United States from 2013-2014 to the current flu season (2023-2024). However, influenza B/Yamagata viruses have not been detected to be actively circulating in global surveillance after March 2020, and therefore, their inclusion in flu vaccines is no longer warranted.

According to an FDA statement: “FDA has been engaging and interacting with manufacturers of FDA-approved seasonal flu vaccines and providing scientific and regulatory advice to them to facilitate the timely availability of approved safe and effective trivalent seasonal flu vaccines for the 2024-2025 U.S. flu season. FDA anticipates that there will be an adequate and diverse supply of approved trivalent seasonal flu vaccines for the United States in the coming season.”

Each year CDC publishes recommendations for the use of flu vaccines in the United States based on input from the Advisory Committee on Immunization Practices. The annual recommendations for the 2024-2025 flu vaccine are expected to publish in August 2024.