Evaluating the impact of influenza vaccination. A North American perspective.

Recent studies in the US and Canada have shown that influenza vaccination prevents approximately 30 to 50% of all pneumonia and influenza hospitalisations and deaths that occur among elderly persons during 3-month influenza outbreak periods. These population-based studies have used retrospective methods and large computerised administrative databases. In addition, earlier cost-effectiveness studies have been supplemented by recent research from prepaid health plans showing that influenza vaccination can be cost saving. The use of influenza vaccine increased in the US and Canada throughout the 1980s and early 1990s, despite different methods for providing reimbursement for vaccination. The North American experience regarding the clinical effectiveness, cost effectiveness and epidemiology of influenza vaccination may provide European scientists and health officials with useful although sometimes limited insight into their own efforts to understand and improve influenza vaccination.