Reference viruses for seasonal and pandemic influenza vaccine preparation

The production of seasonal and pandemic influenza vaccines depends on the timely availability of suitable reference viruses. Seasonal vaccines are traditionally produced from high-growth reassortant viruses, which have been derived empirically using well-established techniques. However, it is not possible to use such approaches in deriving vaccine reference viruses from highly pathogenic H5N1 viruses and alternative techniques such as reverse genetics must be employed.