Effect of prior pneumococcal vaccination on clinical outcome of hospitalized adults with community-acquired pneumococcal pneumonia

The aim of this study was to evaluate the effect of prior pneumococcal vaccination on the clinical outcome of 554 consecutive hospitalized adults with community-acquired pneumococcal pneumonia from 1995 to 2004, 61 of whom had been vaccinated in the 5 years before admission. Outcome variables that were compared in vaccinated and unvaccinated adults included the occurrence of bacteremia, the time to resolution of pneumonia symptoms, the length of hospital stay, and mortality. Prior pneumococcal vaccination was associated with a lower risk of bacteremia (odds ratio 0.46, 95% CI 0.22-0.98). Compared with unvaccinated patients, vaccine recipients had better clinical outcomes, which included a faster resolution of pneumonia symptoms. The median length of hospital stay was shorter in vaccinated patients (8.0 vs. 9.0 days; p=0.032). Overall case-fatality rates did not differ significantly between groups (1.6% vs. 6.2%; p=0.233). In conclusion, prior pneumococcal vaccination appears to be associated with a lower risk of bacteremia, a faster time to resolution of symptoms, and a shorter hospital stay in adults with pneumococcal pneumonia. The findings presented here provide additional support to the current vaccine recommendations and should encourage healthcare providers to increase pneumococcal vaccine coverage among targeted adult populations.