influenza virus type B (Victoria)

Influenza virus type B (Victoria) refers to a specific lineage of the Influenza B virus, known as the Victoria lineage. It is one of two main lineages of Influenza B viruses that have circulated in humans; the other is Yamagata. The Victoria lineage is included as a component in seasonal influenza vaccines due to its role in causing annual flu epidemics. The mechanism of action for vaccines containing this antigen involves stimulating an immune response against the hemagglutinin surface protein of the Victoria-lineage Influenza B virus, thereby providing immunity and reducing disease severity if exposed to circulating strains[1][3][7]. These vaccines are typically formulated as trivalent or quadrivalent preparations and may be produced using egg-based or cell-based methods[2][4][5]. As of 2025-2026, only the Victoria lineage is included among Influenza B components due to apparent extinction of Yamagata-lineage viruses[4][7].

Brand names

FluMist QuadrivalentFluad Tetra

Other names

influenza B Victoria lineageB/Victoria lineage