influenza vaccine (recombinant, quadrivalent)

The quadrivalent recombinant hemagglutinin influenza vaccine is a protein-based seasonal flu vaccine designed to protect against four strains of the influenza virus—two A subtypes and two B lineages. Unlike traditional egg-based vaccines, it uses purified hemagglutinin proteins produced in insect cell cultures via recombinant DNA technology. The process involves inserting the gene for the desired hemagglutinin antigen into a baculovirus vector, which then infects insect cells (*Spodoptera frugiperda*), leading to production and purification of the HA protein for each strain included in the formulation[5][6]. This approach avoids egg allergens and allows rapid adaptation to circulating strains. The primary mechanism of action is induction of an immune response against viral hemagglutinin antigens, resulting in neutralizing antibodies that prevent infection[7]. It is indicated for active immunization against disease caused by included strains in adults 18 years and older[2][3][7]. Clinical studies suggest improved or comparable immunogenicity versus standard-dose inactivated vaccines, especially among older adults or those with egg allergies[1][8].

Brand names

Flublok Quadrivalent

Other names

recombinant hemagglutinin influenza vaccinerHA quadrivalent influenza vaccinerecombinant influenza vaccine (RIV4)Flublok