Pneumococcal vaccine.

Pneumococcal infections are common and serious infections, and their control is an important public health priority. A multivalent pneumococcal vaccine was introduced several years ago, but there is still controversy about its effectiveness in United States populations. One randomized controlled study in high-risk veterans did not demonstrate efficacy. The study has been criticized because the case definitions used for pneumococcal infection had uncertain specificity. Two large case control studies done in Pennsylvania and Connecticut hospitals have compared vaccination rates in patients with pneumococcal bacteremia with controls matched for disease severity and age. Bacteremic immunosuppressed patients who were unlikely to have responded to pneumococcal vaccine were excluded. These studies showed vaccine efficacy rates in the 60% to 70% range as did a prospective randomized controlled French trial that used episodes of pneumonia as an end point. Pneumococcal vaccine is effective when given to patients likely to respond immunologically and who are at increased risk from pneumococcal infection.