Effectiveness of pneumococcal polysaccharide vaccine in older adults

BackgroundStreptococcus pneumoniae is the chief cause of pneumonia in older adults, but it remains unclear whether use of the pneumococcal polysaccharide vaccine alters the overall risk of community-acquired pneumonia. In a large population of older adults, we assessed the effectiveness of the pneumococcal vaccine. MethodsIn this retrospective cohort study, 47,365 Group Health Cooperative members 65 years of age or older were assessed over a three-year period. The primary outcomes were hospitalization because of community-acquired pneumonia (validated by chart review), pneumonia in patients who were not hospitalized (“outpatient pneumonia,” determined from administrative data sources), and pneumococcal bacteremia. The association between pneumococcal vaccination and the risk of each outcome was evaluated by means of multivariate Cox proportional-hazards models, with adjustment for age, sex, nursing-home residence or nonresidence, smoking status, medical conditions, and receipt or nonreceipt of influenza v...