Influenza-Related Causes of Hospitalization in Elderly in Brazil, 1992 to 2006

This ecologic study aims to describe the influenza-related causes of hospitalization in Brazilian people older than 59 years, in the period from 1992 to 2006, using data from the Hospital Information System of the National Health System. The mean annual hospitalization rate (HR) in Brazil was of 22/1,000 elderly population. In the Southern Region, Southeastern and Centre-Western Regions, the greater magnitude of HR has been identified from May to August, while in Northern and Northeastern Regions, it was from February to June. Comparing the average of HR in between prior (1992-1998) and later (1999-2006) periods of introduction of vaccination against influenza, it is observed reduction in the HR in Brazil, especially in the Southern, Southeastern and Centre-Western Regions. The different epidemiological profiles of the disease observed may be influenced by demographic density, age composition and climatic condition. The decrease in rates after 1999 may be related to vaccination campaigns. More studies are necessary to analyze trends of hospitalization rates, and to determine the causal relation to influenza vaccination.