As we look ahead to the 2026 flu season, there is an important shift underway in Australia’s seasonal influenza vaccination strategy. The Australian Technical Advisory Group on Immunisation (ATAGI) and other health authorities have signalled a transition from quadrivalent influenza vaccines (QIV) to trivalent influenza vaccines (TIV). This transition follows the northern hemisphere implementing this change as of the 2024-2025 season.

The quadrivalent vaccines currently protect against four strains of influenza: two A subtypes (H1N1 and H3N2) and two B lineages (Victoria and Yamagata). However, the B/Yamagata lineage has not been detected in circulation globally since March 2020.

Because of this, the World Health Organization (WHO) and Australia’s Influenza Vaccine Committee (AIVC) have deemed that continuing to include the B/Yamagata antigen is no longer necessary. As a result, vaccines that include only one B lineage (i.e. TIVs) are now being recommended and will be the norm moving forward into 2026.