The Burden of Pneumococcal Community-Acquired Pneumonia and Invasive Pneumococcal Disease in Hospitalized Adults: A Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) Network Study

Abstract

Background. Pneumococcal community acquired pneumonia (CAP) and invasive pneumococcal disease (IPD) cause significant morbidity and mortality worldwide. Although childhood immunization programs have reduced the burden of pneumococcal disease, there is insufficient data in Canada to advise immunization policy in adults. This study aimed to describe clinical outcomes of pneumococcal CAP and IPD in hospitalized Canadian adults, and determine the proportion of patients with vaccine-preventable disease. Methods. To establish the burden of pneumococcal disease, active surveillance for CAP and IPD in hospitalized adults was performed in five Canadian provinces from December 2010 to 2013. The serotype distribution was characterized using the Quellung reaction, PCR-based serotyping, and urine antigen detection (UAD). Results. Of 4769 cases of all-cause CAP, a laboratory test for pneumococci was performed in 3703. Of these, 516 (13.9%) were pneumococcal CAP (CAPSpn) and 238 (6.4%) were bacteremic CAPSpn. In addition to CAP, 80 cases of IPD (non- CAP) were identified. The burden of CAPSpn, bacteremic CAPSpn, and IPD was evident in terms of intensive care unit admission, mechanical ventilation, and 30-day mortality. Overall, the proportion of all-cause CAP with laboratory testing identifying a 13- valent pneumococcal conjugate vaccine (PCV13) or 23-valent pneumococcal polysaccharide vaccine (PPV23) serotype was 6.2% and 7.1%, respectively. However, these values are underestimated; 41.9% of the CAPSpn case isolates were not viable upon reculturing, non-typeable, or unavailable for serotyping. Of the available serotypes, PCV13- and PPV23-serotypes represented 76.0% and 87.7% in CAPSpn, respectively. If these proportions are extrapolated to the overall contribution of CAPSpn to all-cause CAP of 13.9%, PCV13- and PPV23-serotypes would represent 10.6% and 12.2% of allcause CAP, respectively. The results of a PCV13-specific UAD were consistent with this estimation at 197/1907 (10.3%). Conclusion. This study demonstrated that pneumococcal CAP and IPD are significant causes of morbidity and mortality in hospitalized Canadian adults, with a large proportion of available S. pneumoniae serotypes being vaccinepreventable.