Quadrivalent influenza vaccine (Sinovac Biotech) for seasonal influenza prophylaxis.

Quadrivalent Influenza Vaccine (Sinovac Biotech) is a quadrivalent split-virion-inactivated influenza vaccine approved in China in June 2020 for individuals ≥3 years of age. It contains 15 µg hemagglutinin per strain including A/H1N1, A/H3N2, B/Victoria, and B/Yamagata, which could potentially improve protection against influenza B viruses. In this review, we summarize the development of quadrivalent influenza vaccines in China and foreign countries, and assess the immunogenicity and safety from the phase I and III clinical trials of Quadrivalent Influenza Vaccine in individuals ≥3 years of age. We also discuss the potential application of Quadrivalent Influenza Vaccine in young children 6-35 months of age according to the results of the phase III trial. The immunogenicity and safety profiles of Quadrivalent Influenza Vaccine containing two A and two B strains were comparable to the trivalent vaccines for the shared strains. The addition of a second B strain to the trivalent vaccine could induce superior immune responses for the alternate B strain. Since the two B strains co-circulated worldwide, the introduction of quadrivalent influenza vaccines has been expected to be a cost-effective strategy.