quadrivalent inactivated influenza vaccine

A synthetic vaccine consisting of hemagglutinin (HA) antigens derived from four inactivated influenza viruses, two different influenza type A strains and two different influenza type B strains, with protective immunizing activity. Quadrivalent influenza vaccine (QIV) is formulated annually, based on influenza strains projected to be prevalent in the upcoming flu season. Upon administration, the QIV provides active immunization against the four influenza virus strains, thereby protecting against influenza infection.