Effectiveness of the pneumococcal polysaccharide vaccine in preventing pneumonia in the elderly

The objective of our study was to evaluate the effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPV) in preventing hospital admission for community-acquired pneumonia (CAP) in people >= 65 yrs of age. We conducted a matched case-control study in patients with CAP admitted to five Spanish hospitals. Cases were persons aged >= 65 yrs admitted to hospital through the emergency department, who presented a clinical and radiological pattern compatible with pneumonia, assessed using established criteria. We matched each case with three control subjects by sex, age (+/- 5 yrs), date of hospitalisation (+/- 30 days) and underlying disease. The study period was May 1, 2005 to January 31, 2007. The PPV immunisation status of cases and controls was investigated. Adjusted ORs for vaccination were calculated using logistic regression analysis. A total of 489 cases and 1,467 controls were included in the final analysis. The overall adjusted vaccination effectiveness for all patients was 23.6% (95% CI 0.9-41.0). The adjusted vaccination effectiveness for immunosuppressed patients was 21.0% (95% CI -18.7-47.5). Our results suggest that the PPV may potentially reduce hospitalisations for pneumonia in the elderly and supports vaccination programmes in this age group.