Vaccine Development: The Development of Avian Influenza Vaccines for Human Use

All three influenza pandemics of the twentieth century can be traced back to avian influenza strains. Recent epidemics of highly pathogenic avian influenza A/H5N1 in Asia have resulted in hundreds of deaths in humans and raise the concern of A/H5N1 becoming the next pandemic strain. If an influenza pandemic were to become imminent, vaccination is likely to be the most effective strategy to mitigate the outbreak and save lives. The fundamental issues involved in addressing this public health threat are discussed in this article. Avian influenza infections are explored with regard to virology, transmission, pathogenesis, immunology, and epidemiology. The public health impacts of prior influenza pandemics are discussed as well as the role of vaccination during these pandemics. The immunologic basis of protection against avian influenza through humoral and cellular immunity, as well as the role of cytokines, is discussed, in addition to the vaccine approaches currently being used to generate protective immunity. Vaccine development issues are explored including those related to the use of different vaccine technologies, the selection of animal models for testing, and alternative methods for propagating and manufacturing influenza vaccine. Finally, pandemic preparedness is discussed including vaccine prioritization.