Impact of influenza vaccination on mortality by respiratory diseases among Brazilian elderly persons

Abstract

OBJECTIVE: Respiratory diseases, especially infectious ones, are becoming increasingly representative in the morbidity and mortality patterns of elderly persons. The aim of the present study was to analyze trends in the mortality by respiratory diseases and to observe the impact of influenza vaccination on mortality rates. METHODS: The study was carried out between 1980 and 2000. Subjects were elderly persons living in the State of São Paulo, and mortality data were obtained from the Mortality Information System of the Brazilian Ministry of Health. This is an ecological time-series study. We analyzed the time trends of standardized mortality rates by infectious diseases, according to age group (60-64, 65-69, 70-74, 75-79, and 80+ years) and sex, using polynomial regression. We estimated confidence intervals for the mean expected response in the years following the intervention. RESULTS: Rates increased for both sexes among the elderly population. After the intervention, we observed a declining trend with respect to mortality indicators. For older males, the mean rate in the 1980-1998 period was 5.08 deaths per thousand men, with a nonlinear, non-constant increase of 0.13 per year; in 2000, the rate observed was 4.72 deaths per thousand men. The mean annual rate among women over 60 years was 3.18 deaths per thousand women, with a nonlinear, non-constant increase of 0.08 per year; in 2000, the rate observed was 2.99 deaths per thousand women. There was also a significant reduction in mortality rates in all age groups. Conclusions: Data indicate the importance of respiratory diseases among the elderly population and suggest that specific protection against influenza has a positive effect on the prevention of mortality due to these diseases.