The Evolving History of Influenza Viruses and Vaccines
Much progress has been made in the 80 years since the isolation of the first influenza virus. Our knowledge about influenza viruses allows us to understand its unpredictability. The influenza A strain has been known to regularly change its antigenic properties, either through minor changes (antigenic drift) or through major changes (antigenic shift). In addition, more than one strain of influenza A can circulate simultaneously. Until recently, it was thought that influenza B did not evolve as much as influenza A, but it is now known that influenza B can undergo major changes and that two strains can circulate simultaneously. This understanding of the evolution of the virus has contributed to the evolution of influenza vaccine from a monovalent live-attenuated vaccine to the latest quadrivalent inactivated vaccine. The need for constant surveillance is recognized and the WHO plays a major role in determining the most likely strains to be circulating and therefore the strains that should be included in the seasonal influenza vaccine.
Expert Commentary
Much progress has been made in the 80 years since the isolation of the first influenza virus. Our knowledge about influenza viruses allows us to understand its unpredictability. The influenza A strain has been known to regularly change its antigenic properties, either through minor changes (antigenic drift) or through major changes (antigenic shift). In addition, more than one strain of influenza A can circulate simultaneously. Until recently, it was thought that influenza B did not evolve as much as influenza A, but it is now known that influenza B can undergo major changes and that two strains can circulate simultaneously. This understanding of the evolution of the virus has contributed to the evolution of influenza vaccine from a monovalent live-attenuated vaccine to the latest quadrivalent inactivated vaccine. The need for constant surveillance is recognized and the WHO plays a major role in determining the most likely strains to be circulating and therefore the strains that should be included in the seasonal influenza vaccine.
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