Background: Although 23-valent polysaccharide pneumococcal vaccine (PPV) does not prevent community-acquired pneumonia (CAP), it might still improve outcomes in those who develop pneumonia. We tested this hypothesis using a population-based cohort of hospitalized patients with CAP.
Methods: From 2000 to 2002, we prospectively collected data on all adults with CAP admitted to 6 hospitals in Capital Health, the largest integrated health delivery system in Canada. Polysaccharide pneumococcal vaccine status was ascertained by interview, medical record review, and contact with physicians and community health offices. The primary outcome was the composite of in-hospital mortality or intensive care unit (ICU) admission. Multivariable regression was used to determine the independent association between PPV use and outcomes, after adjusting for patient characteristics, pneumonia severity, and propensity scores.
Results: Of the 3415 patients with CAP (median age, 75 years), 46% were female, 62% had severe pneumonia, and 22% had prior PPV. Overall, 624 patients died or were admitted to an ICU. Polysaccharide pneumococcal vaccine was protective from reaching this composite end point (73/760 [10%] vs 551/2655 [21%] for unvaccinated patients; P < .001), mostly a result of reduced ICU admission (2/760 [<1%] vs 349/2655 [13%]). The propensity-adjusted odds of death or ICU admission was 0.62 (95% confidence interval, 0.42-0.92; P = .02) for patients who had received PPV. Only 215 of 2416 patients (9%) eligible for PPV at hospital discharge were vaccinated.
Conclusions: Patients with CAP who had prior PPV had about a 40% lower rate of mortality or ICU admission compared with those who were not vaccinated. This provides additional support for recommending PPV to those at risk of pneumonia.