Impact of pneumococcal vaccination on the incidence of pneumonia by HIV infection status among patients enrolled in the Veterans Aging Cohort 5-Site Study.

BACKGROUND Human immunodeficiency virus (HIV)-infected persons have a high incidence of pneumonia and pneumococcal disease. Benefits of vaccination with the 23-valent pneumococcal polysaccharide vaccine (PPV) among these patients continue to be debated. METHODS The impact of PPV vaccination on the incidence of pneumonia events (i.e., the composite of pneumococcal pneumonia and pneumonia due to nonspecified organisms) was examined among participants in the Veterans Aging Cohort 5-Site Study, an ongoing prospective study of HIV-infected patients matched to an HIV-uninfected control group. Dates of PPV vaccination and pneumonia were determined by retrospective review of electronic medical records. Time to events was measured for up to 2 years from PPV vaccination or from enrollment for vaccinated and unvaccinated patients, respectively. Kaplan-Meier and Cox proportional hazards regression methods were used to examine the incidence of pneumonia by HIV infection and PPV vaccination status. RESULTS Among 692 HIV-uninfected and 934 HIV-infected study participants, 59% were vaccinated with PPV. The 2-year incidence of pneumonia was 6% (97 participants developed pneumonia). HIV-infected patients had a higher rate of pneumonia (hazard ratio, 5.81; 95% confidence interval, 3.15-10.71); overall, vaccinated patients showed a trend toward lower risk of pneumonia (hazard ratio, 0.75; 95% confidence interval, 0.50-1.13). Among HIV-infected patients, after controlling for HIV-specific and other variables, vaccination significantly reduced the risk of pneumonia (hazard ratio, 0.65; 95% confidence interval, 0.42-1.00); current smoking, low hemoglobin level, and low CD4 cell count significantly increased such risk. The effect of PPV vaccination among HIV-uninfected patients was not significant. CONCLUSIONS Among HIV-infected patients, PPV vaccination offered protection against pneumonia. Smoking cessation needs to be pursued as an additional strategy for preventing pneumonia.