Australia could switch back to trivalent influenza vaccines by next year after infectious diseases experts deemed the inclusion of one of the four strains in seasonal flu shots “no longer warranted”.

Last year, a WHO expert committee advised against including the B/Yamagata lineage component in flu vaccines because of the absence of confirmed cases since March 2020.

“The absence of confirmed detection of naturally occurring B/Yamagata lineage viruses is indicative of very low risk of infection by B/Yamagata lineage viruses,” it wrote in recommendations for the Southern Hemisphere’s 2024 flu season.

“It is the opinion of the WHO Influenza Vaccine Composition Advisory Committee that the inclusion of a B/Yamagata antigen as a component of influenza vaccines is no longer warranted, and every effort should be made to exclude it as soon as possible.”