2008-2009 Influenza update: a better vaccine match.

Last year, the influenza vaccine did not match the circulating strains very well, and its overall protective efficacy was only 40%. All three antigens contained in the 2008-2009 vaccine are new. Surveillance data from the Southern Hemisphere during the summer of 2008 show that this vaccine is expected to match well the circulating strains in the Northern Hemisphere.