Use of chest radiography examination as a probe for pneumococcal conjugate vaccine impact on lower respiratory tract infections in young children

Background. Community-acquired alveolar pneumonia (CAAP) is considered a bacterial disease, mainly pneumococcal. CAAP rates markedly declined following 7- and 13-valent pneumococcal conjugate vaccine (PCV) introductions worldwide. In contrast, non-CAAP lower respiratory tract infections (NA-LRIs) are generally not considered pneumococcal diseases. We assessed CAAP, NA-LRIs, and overall visits with chest radiograph (CXR) examination rates in the pediatric emergency room in southern Israel before and after PCV implementation. Methods. This was an ongoing, prospective observational study. Our hospital serves a captive population of approximately 75 000 children aged <5 years, enabling incidence calculation. PCV7 and PCV13 were implemented in Israel in July 2009 and November 2010, respectively. All CXRs were analyzed according to the World Health Organization Standardization of Interpretation. We calculated CAAP, NA-LRI, and CXR examinations annual incidences from 2004 to 2017 and incidence rate ratios comparing the PCV13 (2014-2017) with the pre-PCV (2004-2008) periods. Results. Overall, 72 746 CXR examinations were recorded: 14% CAAP and 86% NA-LRI. CAAP, NA-LRI, and CXR examination visit rates declined by 49%, 34%, and 37%, respectively. This pattern was seen in Jewish and Bedouin children (the 2 ethnically distinct populations), with steeper declines observed among Jewish children and children aged >12 months. Conclusions. PCV7/PCV13 implementation resulted in a marked decline in CAAP and overall visits with CXR examination rates in young children. Overall, approximately 14 750 hospital visits with CXR were prevented annually per 100 000 population aged <5 years. These findings suggest that although NA-LRIs are usually not considered pneumococcal, many can be prevented by PCVs.