[Inactivated influenza virus vaccine: the status quo and several new approaches for future application]

Inactivated influenza vaccines were first developed in the 1930s and then, more efficient methods of virus purification and disruption have led to less toxic vaccine, e.g. HA-split vaccine. A program of annual immunization to schoolchildren had been recommended in Japan since 1960. This assumed that the high incidence of influenza morbidity among schoolchildren might play a role in extending influenza in general population. However, due to the lack of detailed data, the public had bee reluctant to accept, especially for healthy children. Accordingly, the Japanese government changed its policy to vaccinate on demand, which resulted in a marked decrease of vaccinees. Several alternative approaches are in progress to produce more efficient vaccines. DNA vaccine, plasmid DNA encoding influenza peptides, seems promising for future application. However, as it will take more years for clinical evaluation, it is urgent to design a protocol to estimate cost-effectiveness of the presently available inactivated vaccine.