Seasonal inactivated influenza virus vaccines.

Inactivated influenza virus vaccines are the primary modality used for prevention of influenza. A system of annual identification of new strains causing illnesses, selections for vaccines, chick embryo growth, inactivation, processing, packaging, distribution and usage has been in place for decades. Current vaccines contain 15 microg of the HA of an A/H1N1, A/H3N2 and B strain and are given parenterally to induce serum anti-HA antibody for prevention of subsequent infection and illness from natural influenza. Reactogenicity is low and protection among healthy older children and adults is good; protection levels are generally lower in young children and the elderly. Needs include ensuring antigenic matches of vaccine and epidemic viruses each season, enhancing immunization rates, and providing new and improved vaccines and immunization approaches for the varied populations and circumstances globally.