trivalent subunit influenza vaccine (egg-based)

The **trivalent subunit influenza vaccine (egg-based)** is a seasonal influenza vaccine produced using eggs and designed to protect against three selected influenza virus strains: two influenza A strains (H1N1 and H3N2 subtypes) and one influenza B strain (Victoria lineage). The vaccine is typically updated annually to match circulating strains. Egg-based manufacturing involves propagating influenza viruses in the allantoic cavity of embryonated hen eggs, followed by harvesting, inactivation, and purification. The vaccine acts by introducing viral antigens (primarily hemagglutinin and neuraminidase proteins, as well as other surface and internal proteins) that stimulate the immune system to develop protective antibodies, thereby reducing the risk of influenza illness and its complications. The trivalent vaccine formulation is periodically adjusted; for example, for the 2025–2026 U.S. influenza season, recommended strains for egg-based production are A/Victoria/4897/2022 (H1N1)pdm09-like virus, A/Croatia/10136RV/2023 (H3N2)-like virus, and B/Austria/1359417/2021 (B/Victoria lineage)-like virus[1][2][3][4].

Other names

trivalent seasonal influenza vaccine (egg-based)TIV (egg-based)egg-based trivalent influenza vaccine