In response to the disappearance of the B/Yamagata strain of flu B virus during the COVID-19 pandemic, the WHO and some national drug regulators have recommended removing it from flu vaccines. However, the International Federation of Pharmaceutical Manufacturers and Associations (IFPMA) argues that a complete transition for Northern Hemisphere flu vaccines will take place in the 2025-2026 cycle, with Southern Hemisphere vaccines following in winter 2026. This change is more complex than it appears due to regulatory and manufacturing challenges.
Flu vaccines typically target four virus types, including two influenza A viruses and two flu B viruses (B/Victoria and B/Yamagata). Including both flu B viruses in vaccines is relatively recent and aimed at improving effectiveness. However, B/Yamagata viruses have been less prevalent and evolving slower than B/Victoria viruses, suggesting their removal from vaccines.
The shift from quadrivalent to trivalent vaccines is complicated by regulatory requirements across different countries and the need for revalidation and approval of manufacturing processes. The transition involves significant logistical hurdles, with approximately 350 trivalent vaccine licenses needing updates and coordination with about 170 regulatory agencies.
The IFPMA advocates for a synchronized global shift to avoid supply issues. While some experts believe the U.S. could transition faster due to existing regulatory frameworks, the FDA and vaccine manufacturers are still discussing the specifics of this change. The situation will likely become more apparent after the WHO’s meeting in February, where strain selections for the following flu vaccines are determined.
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[Source: STAT, January 16th, 2024]