Vaccination Against Influenza in the Elderly in the City of São Paulo, Brazil: Coverage and Associated Factors

INTRODUCTION: The objective of this study was to estimate the coverage of influenza vaccination among the elderly, and to assess which factors may have contributed to the decision of being vaccinated. 

METHODS: We conducted a cross-sectional population-based study assessing a representative sample of individuals aged 60 or more years old who lived in São Paulo/SP, Brazil. A total of 1,399 elderly men and women answered a structured questionnaire on socio-demographic characteristics, behavior, health status and use of health services. The outcome variable was the self-report of having been vaccinated against influenza in 2006. Data analysis was weighted according to the original cluster sample design. Poisson regression models were used to assess factors associating with the outcome. 

RESULTS: 73.8% of participants reported having been vaccinated in 2006. Characteristics that were associated with a higher prevalence of vaccination in the final model were: age 70-79 years (Prevalence Ratio PR=1.13, 95% Confidence Interval 95%CI=1.06-1.21), 80 years and older (PR=1.11, 95%CI=1.02-1.21), having had a chronic diseases during the previous period of twelve months (PR=1.13, 95%CI=1.01-1.27), two or more chronic diseases (PR=1.18, 95%CI=1.06-1.32) and having received health care during the previous year (PR=1.40, 95%CI=1.08-1.80). One only characteristic associated negatively with the outcome: having been hospitalized during the previous year reduced the prevalence of vaccination (PR=0.84, 95%CI:0.75-0.96). All covariates assessing socioeconomic status were not associated with vaccination. 

CONCLUSIONS: Factors associating with influenza vaccination in the elderly have a multidimensional structure, congregating demographic characteristics, health status and use of health services. Results presented here suggest that the access to vaccination does not differ among social strata in the Brazilian context. These results highlight the need of implementing vaccination among the elders aged less than 70 years old, as well as to instruct health professionals to expand vaccination coverage in groups with lower adherence to the yearly campaigns.