The impact of influenza vaccination on morbidity and mortality in the elderly in the major geographic regions of Brazil, 2010 to 2019.

Due to the importance of annual flu vaccination in the elderly, the study aimed to analyze the impact of influenza vaccination on morbidity and mortality from influenza in the elderly from 2010 to 2019 in the major geographic regions of Brazil. This is an ecological epidemiological study with data from the Information System of the National Immunization Program, Hospital Information System, and Mortality Information System, available from the Brazilian Ministry of Health. Data referred to Brazil and its five major regions and included influenza vaccination coverage rates in the elderly and morbidity and mortality from causes related to influenza and pneumonia in the elderly. Simple linear regression models were used to study the relationship between morbidity and mortality and vaccination coverage rates. There was an increase in vaccination coverage during the period, and the target of 80% coverage was reached in all the regions since 2011. A directly proportional statistical association was identified between the study variables, and the increase in vaccination coverage was associated with an increase in morbidity and mortality from the target causes. These data may be related to reports in the literature showing that the vaccine's effect is modest in the elderly. However, the rates' calculation does not take the population's aging into account, using data from outdated census estimates. Besides, the hospitalization and mortality data may include other circulating viruses and bacteria besides influenza. The maintenance of high vaccination coverage may prevent the impact of influenza from being even higher on morbidity and mortality in the elderly.