Lancet
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Pneumonia is a common complication of influenza infection in elderly individuals and could therefore potentially be prevented by influenza vaccination. In studies with data from administrative sources, vaccinated elderly people had a reduced risk of admission for pneumonia compared with unvaccinated seniors; however, these findings could have been biased by underlying differences in health between the groups. Furthermore, since most individuals with pneumonia are not treated in hospital, such studies should include both outpatient and inpatient events. We therefore assessed whether influenza vaccination is associated with a reduced risk of community-acquired pneumonia in immunocompetent elderly people after controlling for health status indicators. ⋯ Group Health Center for Health Studies internal funds and Group Health Community Foundation fellowship grant.