ORIGINAL INVESTIGATION Impact of Influenza Vaccination on Seasonal Mortality in the US Elderly Population

enza vaccination reduces winter mortality risk from any cause by 50 % among the elderly. Influenza vaccination cov-erage among elderly persons (65 years) in the United States increased from between 15 % and 20 % before 1980 to 65 % in 2001. Unexpectedly, estimates of influenza-related mortality in this age group also increased during this period. We tried to reconcile these conflicting find-ings by adjusting excess mortality estimates for aging and increased circulation of influenza A(H3N2) viruses. Methods: We used a cyclical regression model to gen-erate seasonal estimates of national influenza-related mor-tality (excess mortality) among the elderly in both pneu-monia and influenza and all-cause deaths for the 33 seasons from 1968 to 2001. We stratified the data by 5-year age group and separated seasons dominated by A(H3N2