Emulsion-based adjuvants for influenza vaccines.

The ongoing epizootic of highly pathogenic avian H5N1 influenza and its direct transmissibility and high pathogenicity in humans has led to renewed interest in the development of influenza vaccines with enhanced immunogenicity. Influenza vaccines are currently under development against influenza strains that are potentially pandemic threats, such as H5N1, as well as against the current seasonal influenza strains for use in populations susceptible to severe influenza disease. Influenza vaccines may be generally divided into two types: seasonal vaccines for use in a population that is largely primed to subtypes of the circulating influenza A strains and pandemic influenza vaccines that are designed to protect against influenza A viruses of a hemagglutinin (HA) subtype, to which the vast majority of the population is immunologically naive.