bivalent 6:2 influenza virus reassortant vaccine

The bivalent 6:2 influenza virus reassortant vaccine is an investigational live-attenuated influenza vaccine (LAIV) formulation developed by MedImmune (a subsidiary of AstraZeneca). It is primarily used in annual safety bridging studies to evaluate new seasonal influenza strains before their inclusion in the quadrivalent FluMist (LAIV4) vaccine. The "6:2" designation refers to the genetic architecture of the vaccine viruses, which are engineered to contain six internal gene segments from a cold-adapted, temperature-sensitive, and attenuated master donor virus (MDV)—typically A/Ann Arbor/6/60 for type A strains and B/Ann Arbor/1/66 for type B strains—and two surface protein gene segments (hemagglutinin and neuraminidase) derived from the target seasonal wild-type strains. This reassortment process ensures that the vaccine viruses are restricted to replicating in the cooler environment of the upper respiratory tract, inducing mucosal and systemic immunity without causing systemic disease. The bivalent formulation allows for the targeted safety assessment of the two newly updated strains for a specific influenza season, as required by regulatory authorities for the annual update of the live-attenuated vaccine product.

Brand names

FluMist

Other names

LAIV bivalent6:2 reassortant influenza vaccinebivalent live-attenuated influenza vaccine