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CSL Adopts Regional/National Public Health Timetable on the Removal of B/Yamagata Seasonal Influenza Virus Strain

March 7, 2024

During the latter part of 2023 and following notification by the World Health Organization that B/Yamagata lineage viruses have not been confirmed as detected in circulation since the beginning of the pandemic, health authorities across the world have recommended its removal from seasonal influenza vaccines.1

As a global leader in the protection of public health, CSL has responded swiftly to this guideline and is working in partnership with health authorities to meet the timeline desired by each country for the removal of B/Yamagata from our influenza vaccines. This means that for the U.S., our transition from quadrivalent to trivalent influenza vaccines will take place in time for the ‘24/’25 season.  For other countries, we are continuing to consult on the most optimal timing. 

By collaborating with public health stakeholders on an appropriate timetable in country, we aim to ensure a smooth transition, increase vaccine confidence and improve immunization rates across the globe.

Importantly, the disappearance of B/Yamagata is a testament to the role of widely implemented influenza immunization programs, amongst other contributing factors such as the inherent characteristics and epidemiology of the B/Yamagata virus and the unique environment created by the COVID-19 pandemic.2




1 Kondor, Rebecca (2023). Update on Influenza B/Yamagata Surveillance. Slide 13. World Health Organization.
2 Koutsakos, M., Wheatley, A. K., Laurie, K., Kent, S. J., & Rockman, S. (2021). Influenza lineage extinction during the COVID-19 pandemic? Nature Reviews Microbiology, 19(12), 741-742.

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