CSL Seqirus is Fully Prepared to Implement the FDA’s Vaccines and Related Biological Products Advisory Committee Trivalent Influenza Vaccines Strain Selection for the 2024/25 U.S. Season

CSL Seqirus, a global leader in the protection of public health, confirmed it is fully prepared to deliver its influenza vaccine portfolio for the 2024/25 U.S. season, based on the trivalent strains recommended this week by the U.S. Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee.

SUMMIT, N.J., March 6, 2024 /PRNewswire/ -- CSL Seqirus, a global leader in the protection of public health, confirmed it is fully prepared to deliver its influenza vaccine portfolio for the 2024/25 U.S. season, based on the trivalent strains recommended this week by the U.S. Food and Drug Administration’s (FDA) Vaccines and Related Biological Products Advisory Committee (VRBPAC). During the meeting, the committee confirmed the viral strain selection of influenza vaccines for the Northern Hemisphere 2024/25 season, which aligns with the February 2024 World Health Organization (WHO) annual recommendations and is unchanged from the Southern Hemisphere 2024 season.1

“CSL Seqirus applauds the VRBPAC’s commitment to providing a clear, evidence-backed recommendation to the FDA so that the composition of seasonal influenza vaccines for the upcoming season will be formulated to match projected circulating strains, based on the WHO’s ongoing surveillance,” said Gregg Sylvester, Chief Health Officer and Head of Medical Affairs, CSL Seqirus. “In addition to implementing this change, we are committed to working with our partners in public health to reverse the alarming decline in immunization rates and vaccine confidence that we have seen over the past two flu seasons.”

The VRBPAC’s recommendation follows the October 2023 VRBPAC meeting, where the committee strongly supported the WHO’s recommendation to expeditiously remove the B/Yamagata influenza virus strain from quadrivalent influenza vaccines and transition to trivalent influenza vaccines for the 2024/25 season.2 The recommendation was grounded in data from the WHO’s global influenza response and surveillance system, which detected a decline in B/Yamagata circulation before the onset of the COVID-19 pandemic and no further circulation of B/Yamagata lineage viruses since March of 2020.3

The strain selection for the 2024/25 influenza season reflects the removal of B/Yamagata and it will not be included in the vaccines manufactured and delivered by CSL Seqirus. CSL Seqirus worked closely with the FDA during 2023 to align on a path forward and is fully prepared to transition its complete portfolio of seasonal influenza vaccines in the U.S. market from quadrivalent to trivalent formulations for the 2024/25 influenza season. CSL Seqirus completed its transition plan for the 2024/2025 season by December 2023 and regulatory and manufacturing teams are on track to convert the full U.S. portfolio. As a result of this effort, CSL Seqirus received FDA approval on March 4, 2024 for all of its U.S. trivalent influenza vaccines.

“This strain consistency across hemispheres will support both speed and efficiency, as CSL Seqirus has experience manufacturing these recommended strains,” said Dave Ross, Vice President, North America Commercial Operations, CSL Seqirus.

Across the world, CSL Seqirus is collaborating with regulatory bodies and public health authorities on an appropriate transition timeline for each country that aims to ensure a smooth transition, increase vaccine confidence and improve immunization rates.

The undetectable circulation of B/Yamagata is a testament to the critical 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.3

The VRBPAC is the FDA’s advisory committee of experts in the fields of immunology, molecular biology, rDNA, virology bacteriology, epidemiology or biostatistics, vaccine policy, vaccine safety science, federal immunization activities, vaccine development including translational and clinical evaluation programs, allergy, preventive medicine, infectious diseases, pediatrics, microbiology, and biochemistry.4 VRBPAC reviews and evaluates data concerning the safety, effectiveness, and appropriate use of vaccines and related biological products which are intended for use in the prevention, treatment, or diagnosis of human diseases, and, as required, any other products for which the FDA has regulatory responsibility.4

About Seasonal Influenza
Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life-threatening complications in some people.5 Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalization and in some cases, death. Because transmission of influenza viruses to others may occur one day before symptoms develop and up to 5 to 7 days after becoming sick, the disease can be easily transmitted to others.5 Preliminary estimates from the Centers for Disease Control and Prevention (CDC) report that during the 2023/24 influenza season, there have been an estimated 290,000-610,000 influenza-related hospitalizations in the U.S.6 The CDC recommends annual vaccination for individuals aged 6 months and older, who do not have any contraindications.7 Since it takes about two weeks after vaccination for antibodies to develop in the body that help protect against influenza virus infection, it is recommended that people get vaccinated before influenza begins spreading in their community.7 The CDC recommends that for most people who need only 1 dose of flu vaccine, vaccination should ideally happen in September or October.7

About CSL Seqirus
CSL Seqirus is part of CSL (ASX: CSL). As one of the largest influenza vaccine providers in the world, CSL Seqirus is a major contributor to the prevention of influenza globally and a transcontinental partner in pandemic preparedness. With state-of-the-art production facilities in the U.S., the U.K. and Australia, and leading R&D capabilities, CSL Seqirus utilizes egg, cell and adjuvant technologies to offer a broad portfolio of differentiated influenza vaccines in more than 20 countries around the world.

For more information about CSL Seqirus, visit CSL.com/CSLSeqirus.

About CSL
CSL (ASX: CSL) (USOTC: CSLLY) is a global biotechnology company with a dynamic portfolio of lifesaving medicines, including those that treat haemophilia and immune deficiencies, vaccines to prevent influenza, and therapies in iron deficiency and nephrology. Since our start in 1916, we have been driven by our promise to save lives using the latest technologies. Today, CSL – including our three businesses: CSL Behring, CSL Seqirus and CSL Vifor – provides lifesaving products to patients in more than 100 countries and employs 32,000 people. Our unique combination of commercial strength, R&D focus and operational excellence enables us to identify, develop and deliver innovations so our patients can live life to the fullest. For inspiring stories about the promise of biotechnology, visit CSL.com/Vita and follow us on Twitter.com/CSL.

For more information about CSL, visit www.CSL.com.

Intended Audience
This press release is issued from CSL Seqirus in Summit, New Jersey, USA and is intended to provide information about our global business. Please be aware that information relating to the approval status and labels of approved CSL Seqirus products may vary from country to country. Please consult your local regulatory authority on the approval status of CSL Seqirus products.

Forward-Looking Statements
This press release may contain forward-looking statements, including statements regarding future results, performance or achievements. These statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements.


Tiffany Cody
+1 (908) 370-1863


1 Food and Drug Administration (FDA). Center for Biologics Evaluation and Research. 184th Vaccines and Related Biological Products Advisory Committee. March 2024. Retrieved from: https://www.fda.gov/advisory-committees/advisory-committee-calendar/vaccines-and-related-biological-products-advisory-committee-march-5-2024-meeting-announcement. Accessed March 2024.
2 FDA. Center for Biologics Evaluation and Research. 183rd Vaccines and Related Biological Products Advisory Committee. Challenges and Opportunities for Vaccine Strain Composition with the Reduced Public Health Threat from Influenza B/Yamagata Lineage Viruses. Slide 7. October 2023. Retrieved from: https://www.fda.gov/media/172762/download. Accessed March 2024.
3 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. https://doi.org/10.1038/s41579-021-00642-4.
4 FDA. Center for Biologics Evaluation and Research. Vaccines and Related Biological Products Advisory Committee. (2019). Retrieved from: https://www.fda.gov/advisory-committees/blood-vaccines-and-other-biologics/vaccines-and-related-biological-products-advisory-committee. Accessed March 2024.
5 Centers for Disease Control and Prevention (CDC). (2022). Key Facts About Influenza (Flu). Retrieved from: https://www.cdc.gov/flu/about/keyfacts.htm. Accessed March 2024.
6 CDC. (2024). 2023-2024 U.S. Flu Season: Preliminary In-Season Burden Estimates. Retrieved from: https://www.cdc.gov/flu/about/burden/preliminary-in-season-estimates.htm. Accessed March 2024.
7 CDC. (2024). Who Needs a Flu Vaccine. Retrieved from: https://www.cdc.gov/flu/prevent/vaccinations.htm. Accessed March 2024.

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