Quadrivalent influenza vaccine hemagglutinin antigens (QIV HA) (QIV HA)

Hemagglutinin (HA) is the primary surface glycoprotein of influenza A and B viruses, playing a critical role in viral pathogenesis by mediating binding to host cell sialic acid receptors and facilitating subsequent membrane fusion (Source: NIH, 2023). The quadrivalent influenza vaccine (QIV) contains HA antigens from four distinct viral strains—typically two influenza A subtypes (H1N1 and H3N2) and two influenza B lineages (Victoria and Yamagata)—to provide broad protection against seasonal circulating viruses (Source: CDC, 2024). These HA antigens serve as the primary immunogens, stimulating the host immune system to produce neutralizing antibodies that target the HA head or stem regions (Source: StatPearls, 2023). By binding to the HA protein, these antibodies effectively prevent the virus from initiating infection in the respiratory epithelium. Because influenza viruses undergo continuous antigenic drift, the specific HA sequences included in the vaccine are reviewed and updated annually by the World Health Organization based on global surveillance data (Source: WHO, 2024). This target is the cornerstone of global seasonal influenza prophylaxis and is essential for reducing influenza-related morbidity and mortality.

Other names

Quadrivalent influenza vaccineQIVInfluenza A and B hemagglutininHA antigensSeasonal influenza vaccine antigensFour-strain influenza vaccine antigens

Induction of active immunity via the production of neutralizing antibodies that bind to the hemagglutinin protein, thereby blocking viral attachment to host sialic acid receptors and preventing viral entry into host cells.