Changing Epidemiology of Community-Acquired Pneumonia in the Era of Extended Serotype-Covering Multivalent Pneumococcal Conjugate Vaccines

Background: With high pneumococcal vaccine uptake rates in South Korea, the burden of community-acquired pneumonia (CAP) and serotype distribution of pneumococcal CAP may change. Methods: From September 2015 to August 2017, a prospective cohort study was conducted for Korean adults aged ≥ 19 years who were hospitalized with CAP at four university hospitals. All-cause and pneumococcal CAP incidence and mortality rates were evaluated based on the hospital catchment population. Pneumococcal CAP was identified by culture and BinaxNOW urinary antigen test. A newly developed 24 serotype-specific urinary antigen detection (UAD) assay was also used. Findings: Among 2,669 patients with medically attended CAP, 252 cases (9.4%) were pneumococcal CAP. Pneumococcal serotypes were determined in 107 cases. Annual incidence of all-cause and pneumococcal CAP were 194.3 cases and 18.3 cases per 100,000 persons, respectively. Pneumococcal CAP caused by PCV13 and PPSV23 serotypes comprised 46.7% and 77.6% of all serotypable S. pneumonia, respectively. The most prevalent serotype was 3 (19.6%), followed by 19A (9.3%) and 11A (9.3%). The overall 30-day mortality rate of pneumococcal CAP was higher than that of all-cause CAP (6.3% versus 5.7%), but the opposite was found in patients aged 65–74 years (4.2% versus 8.1%) Interpretation: Indirect herd effect from pediatric vaccination might be insufficient. To better control adult CAP, age- and risk-targeted individual PCV13 vaccination should be considered. PPSV23 might decrease the severity of pneumococcal pneumonia, thereby lowering the mortality rate in elderly patients aged 65–74 years. Funding Statement: This work was supported by a Korea University Guro Hospital grant (no. K1719481) that was underwritten by Pfizer. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study was conducted after approval by Institutional Review Boards at each participating study hospital.