Influenza vaccination among the elderly Spanish population:: trend from 1993 to 2003 and vaccination-related factors*

Background: Influenza is an important public health problem that particularly affects elderly subjects and influenza vaccination is a safe, effective and efficient method for prevention of influenza-related complications in elderly individuals with or without underlying chronic conditions. This study aims to analyze adjusted time trends in the coverage of influenza vaccination among elderly Spanish subjects and to identify which variables were associated with the probability of having been vaccinated in 2003. Methods: We undertook a cross-sectional study using data of individuals aged :65 years drawn from the 1993, 1995, 1997, 2001, and 2003 Spanish National Health Surveys. The answer to the question 'Did you have a 'flu shot in the latest campaign' was used as the dependent variable, and socio-demographic and health-related characteristics were analyzed as independent variables. Coverage of vaccination for each year was adjusted by the direct method for both age and gender. Multivariate logistic regression was used to estimate the independent effect of variables on the receipt of influenza vaccine. Results: 15 989 records were analyzed. Adjusted influenza coverage increased from 50.1% in 1993 to 63.7% in 2003 (P < 0.001). The variables that were significantly associated with a higher likelihood of being vaccinated were older age, suffering a chronic disease, residence in towns with < 10000 inhabitants, 'worse' self-perceived health and non-smokers. Conclusions: Coverage among the Spanish elderly has increased significantly from 1993 to 2003. Still, there is room for improvement, particularly, among the subjects with 'good' self-perceived health, those with no concomitant medical conditions, and smokers.