Effects of annual influenza vaccination on winter mortality in elderly people with chronic heart disease

Although there is general agreement for the recommendation of the influenza vaccine to elderly and high-risk adults, the magnitude of clinical effectiveness and benefit from the annual vaccination is controversial. In this study, we have assessed the effects of annual influenza vaccination on winter mortality in older adults with chronic heart disease. Cohort study that included 1340 Spanish community-dwelling individuals 65 years or older who had chronic heart disease (congestive heart failure or coronary artery disease) followed from January 2002 to April 2005. Annual influenza vaccine status was a time-varying condition and primary outcome was all-cause death during the study period. Multivariable Cox proportional-hazard models adjusted by age, sex, and comorbidity were used to evaluate vaccine effectiveness. Influenza vaccination was associated with a significant reduction of 37% in the adjusted risk of winter mortality during the overall period 2002-2005. The attributable mortality risk reduction in vaccinated people was 8.2 deaths per 1000 person-winters. We estimated that one death was prevented for every 122 annual vaccinations (ranging between 49 in Winter 2005 and 455 in Winter 2003). Our results suggest a benefit from the influenza vaccination and support an annual vaccination strategy for elderly people with cardiac diseases.