CDC Says US Will Transition to Trivalent Vaccines Next Flu Season

Earlier this month, the FDA’s Vaccines and Related Biological Products Advisory Committee recommended that all US flu vaccines transition from quadrivalent to trivalent vaccines for the 2024-2025 flu season.¹

The trivalent vaccines’ formula will still contain the influenza A(H1N1), A(H3N2), and B/Victoria-lineage vaccine virus, but omit the influenza B/Yamagata virus because it is no longer actively circulating.

“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 US flu season,” said the FDA in a news release.² “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, scientists review and update the composition of the US flu vaccine to target the strains predicted to be most prevalent in the coming flu season. Based on past reviews, this will not be the first time that patients seeking flu shots will be given trivalent vaccines.

READ MORE: How Will the Extinction of B/Yamagata Impact Global Flu Vaccination Strategies?

Starting with the 1978-1979 season through the 2012-2013 season, US flu vaccines contained 3 vaccine viruses: influenza A(H1N1), A(h3N2), and a B-lineage vaccine virus either from the B/Yamagata or B/Victoria lineage.¹ Quadrivalent flu vaccines first became available in the US during the 2013-2014 flu season and have remained as the standard composition until the current flu season (2023-2024).¹

Transitioning from quadrivalent to trivalent vaccines will increase the current production capability by 200 million doses, allowing more patients to be vaccinated from the flu.³ This expansion in access may help alleviate the substantial health burden that the flu exacts on the US— this past flu season was classified as moderate severity for adults and high severity for children by the CDC⁴—as well as mitigate vaccine shortages and distribution inequities often experienced by developing countries.³

Each year, the virus causes millions of infections, hundreds of thousands hospitalized, and billions of dollars lost in health care costs and missed days of work.³

Vaccines, which have been long considered a first-line defense against the flu, have been recommended in the US for more than 50 years for everyone 6 months and older, with rare exception.¹ They have been clinically proven to reduce the severity of the virus and the risk of developing potentially serious complications.

Some experts say that public health measures to curb the spread of SARS-COV-2 during the COVID-19 pandemic, such as lockdowns, travel restrictions, and mask mandates, might have unintentionally reduced the spread of Yamagata B.³ The strain had not been detected to be actively circulating in global surveillance after March 2020,¹ suggesting these measures may have halted its circulation entirely.

Since changes in vaccine composition can sometimes lead to confusion or misinformation, effective communication, such as that conducted through public health campaigns or physician-patient discussions, is crucial to promote vaccine uptake.⁵ Health care providers and public health officials can ensure patient safety by explaining the rationale behind the composition change and emphasizing trivalent vaccines’ continued effectiveness against the flu.

READ MORE: Immunization Resource Center

References

1. US will transition to trivalent flu vaccines for 2024-2025. News release. CDC. March 8, 2024. Accessed March 13, 2024. https://www.cdc.gov/flu/spotlights/2023-2024/trivalent-vaccines-2024-2025.htm#:~:text=The%20Committee%20recommended%20that%20all,%2FVictoria-lineage%20vaccine%20virus.

2. Use of trivalent influenza vaccines for the 2024-2025 US influenza season. News release. FDA. March 5, 2024. Accessed March 13, 2024. https://www.fda.gov/vaccines-blood-biologics/lot-release/use-trivalent-influenza-vaccines-2024-2025-us-influenza-season

3. Vajo Z, Torzsa P. Extinction of the influenza B Yamagata line during the COVID pandemic-Implications for vaccine composition. Viruses. 2022;14(8):1745. doi:10.3390/v14081745

4. White EB, O'Halloran A, Sundaresan D, et al. High influenza incidence and disease severity among children and adolescents aged <18 years - United States, 2022-23 Season. MMWR Morb Mortal Wkly Rep. 2023;72(41):1108-1114. doi:10.15585/mmwr.mm7241a2

5. Meara K. How will the extinction of B/Yamagata impact global flu vaccination strategies? News article. Drug Topics. February 13, 2024. Accessed March 13, 2024. https://www.drugtopics.com/view/how-will-the-extinction-of-b-yamagata-impact-global-flu-vaccination-strategies-