How are the viruses selected to make flu vaccine?
The influenza (flu) viruses selected for inclusion in the seasonal flu vaccines are updated each year based information about which influenza virus strains are identified, how they are spreading, and how well current vaccine strains protect against newly identified strains. Currently, 130 national influenza centers in 101 countries conduct year-round surveillance for influenza and study influenza disease trends. These laboratories then send influenza viruses to the four World Health Organization (WHO) Collaborating Centers for Reference and Research on Influenza located in Atlanta, Georgia, USA (Centers for Disease Control and Prevention, CDC); London, United Kingdom (National Institute for Medical Research); Melbourne, Australia (Victoria Infectious Diseases Reference Laboratory); Tokyo, Japan (National Institute for Infectious Diseases) for additional analyses. The seasonal flu vaccine is a trivalent vaccine (a three component vaccine) with each component selected to protect against
