A controlled evaluation of the protective efficacy of pneumococcal vaccine for patients at high risk of serious pneumococcal infections.

The protective efficacy of pneumococcal vaccine against systemic pneumococcal infections in adults with the current indications for the vaccine was evaluated in a case-control study. Six (7%) of the 90 cases and 16 (18%) of the matched controls had received pneumococcal vaccine for an odds ratio of 0.33 (p less than 0.05). The vaccine's protective efficacy was 67%, which remained virtually unchanged after adjusting for potential confounding variables. The vaccine's efficacy was 77% for patients at moderately increased risk of pneumococcal infections, but 0% for patients who were severely immunocompromised. The vaccine's protective efficacy was 70% (p less than 0.05) for all patients 55 years or older after controlling for indications for the vaccine in addition to age. Pneumococcal vaccine confers substantial protection against systemic pneumococcal infections on the elderly and patients with illnesses associated with a moderately increased risk of pneumococcal infections.