[Pandemic and prepandemic H5N1 influenza vaccines: a 2009 update]

Since 2003, hundreds of infections with H5N1 avian influenza virus have been reported in humans with a mortality rate of ca. 60 %, which makes us fear a pandemic influenza in a population without pre-existing immunity. Currently, the inter-human transmission is limited to persons in close contact with poultry. In anticipation of this pandemic threat, a global plan was established in which immunization represents a major issue. However, the development of a vaccine is related to many specific problems as the manipulation of strains or evaluation of immunogenicity. In addition, production delays after identification of the pandemic virus are incompressible and the pandemic is likely to develop before a vaccine is available. Specific approaches have been developed to produce prepandemic vaccines that can induce cross-immunity, partially effective on the pandemic strain. In 2009, several prepandemic and pandemic vaccines have obtained their licensure authorization and strategies are being developed in case of pandemic influenza.