Pneumococcal conjugate vaccine use among young children has led to significant declines in invasive pneumococcal disease in the United States, but the impact on community-acquired pneumonia is unknown. We conducted population-based pneumonia surveillance among 794,282 Group Health members before and after infant vaccine introduction in 2000. We presumptively identified pneumonia episodes using diagnosis codes assigned to medical encounters and confirmed 17,513 outpatient and 6318 hospitalized events by reviewing chest radiograph reports or hospitalization records. There was evidence for a decline in rates of both outpatient and hospitalized pneumonia in children less than 1 year of age following vaccine introduction but there were no consistent reductions in pneumonia rates among older children and adults.