When the World Health Organization recommended Friday which influenza viruses should be targeted for next year’s vaccines, it excluded a virus family not seen since the early days of the COVID-19 pandemic.
When the novel coronavirus disease (Covid-19) began to spread widely in 2020, people took protective measures such as wearing masks, washing hands, and avoiding contact with others, and influenza infections plummeted. Although influenza recovered, the virus family known as influenza B/Yamagata did not, suggesting it may have been driven to extinction.
For the future 2024 Southern Hemisphere influenza season, experts advising the WHO on Friday recommended a trivalent vaccine that targets three types of influenza, including the two influenza A strains, H1N1 and H3N2, and the influenza B/Victoria strain. A quadrivalent vaccine that targets four types of influenza can also target components of the B/Yamagata lineage.
WHO advisers said at a press conference on Friday that B/Yamagata has not been identified in years, so there is no benefit in including it in vaccines.
David Wentworth, director of the Collaborating Center for Influenza Surveillance, Epidemiology and Control, said: “I’m not saying it’s a bad thing for it to be in vaccines, it’s just that it doesn’t need to be in vaccines at this point and there’s no guarantee that it will.” Stated. he said at a press conference at the U.S. Centers for Disease Control and Prevention. “So our recommendation was to remove that component.”
Viruses continually evolve, so influenza vaccines are updated regularly. While the WHO recommendations are a guide for regulators and manufacturers around the world, the final decision on which components to include is made by each country. WHO recommendations for the Southern Hemisphere are usually made in September, and recommendations for the Northern Hemisphere in February. These schedules allow sufficient time for regulatory approval and vaccine manufacturing and distribution ahead of each hemisphere’s influenza season.
In their report on the 2024 Southern Hemisphere influenza vaccine recommendations, WHO advisors also considered that the use of B/Yamagata virus in vaccine production poses a “theoretical risk of reintroduction into the population.” Removing B/Yamagata from vaccines could reduce the theoretical risk, the researchers wrote.
“We are balancing the lack of circulating Yamagata-lineage viruses with the theoretical risk of manufacturing and using unnecessary ingredients,” Peter Center Influenza Reference・Kanta Subbarao, director of the Research Cooperation Center, said: Doherty Institute of Infection and Immunology, Australia.
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The vaccines being administered in the United States during the current influenza season are quadrivalent vaccines for two influenza A viruses, H1N1 and H3N2, and two influenza B viruses, including the Yamagata strain. evidence The early season in the Southern Hemisphere suggests it is well suited to the virus that will be prevalent this fall and winter.
WHO advisors stressed that influenza vaccines are safe and effective, no matter which formulation a country uses. Wentworth said the U.S. Food and Drug Administration is considering whether to move to a trivalent vaccine for the upcoming influenza season, but given the necessary approvals and manufacturing changes, it won’t be an overnight change. Stated.
of FDA Vaccine Advisory Committee will meet on October 5 to discuss recommendations for an influenza vaccine to be provided in the Southern Hemisphere in 2024.