Why does it take so long to make a vaccine against a new influenza virus variant?
The first decision that has to be made is: which vaccine? Vaccines that are used against seasonal influenza are based on the three most prevalent circulating influenza viruses. A comprehensive, international ‘virus-watch’ program based administratively in WHO Geneva co-ordinates the operations of four WHO Collaborating Centers (London, Melbourne, Tokyo, Atlanta) and a host of National Laboratories. A combination of RT-PCR and rapid sequencing is used for the rapid characterization of viruses in human circulation and that information is made available globally. A key WHO committee meets twice each year to decide which influenza A and B viruses will be included in the three-component (H1N1, H3N2, influenza B) vaccines manufactured commercially for use in the Northern and Southern hemispheres. Of course, this dynamic changes immediately when a new virus, like the current ‘swine’ H1N1, suddenly enters the human population raising the possibility that a new vaccine must be produced. The mos
