Abstract
BACKGROUND: Pneumonia is the most serious form of acute respiratory infection and Streptococcus pneumoniae is a leading cause of pediatric bacterial pneumonia. Pneumococcal conjugate vaccines were introduced in the United States (US) in 2000 (7-valent [PCV7]) and 2010 (13-valent [PCV13]). This study estimated annual incidence rates (IRs) of all-cause pneumonia (ACP) among US children aged < 18 years before and after the introduction of PCV7 and PCV13. METHODS: ACP episodes were identified in the IBM MarketScan Commercial and Medicaid Databases using diagnosis codes. Annual IRs were calculated overall and by inpatient and outpatient settings as the number of episodes per 100,000 person-years (PY) for all children aged < 18 years and by age group (< 2, 2-4, and 5-17 years). National estimates of annual pneumonia IRs were extrapolated using Census Bureau data. Interrupted time series (ITS) analyses were used to assess immediate and gradual changes in monthly pneumonia IRs, adjusting for seasonality. RESULTS: In the commercially-insured population, ACP IRs declined between the pre-PCV7 period (1998-1999) and late PCV13 period (2014-2018) from 5,322 to 3,471 episodes per 100,000 PY for children aged < 2 years, from 4,012 to 3,794 episodes per 100,000 PY in children aged 2-4 years but increased slightly from 1,383 to 1,475 episodes per 100,000 PY in children aged 5-17 years. The ITS analyses indicated significant decreases in monthly ACP IRs in the early PCV7 period (2001-2005) among younger children and in the early PCV13 period (2011-2013) among all children. Increases were observed in the late PCV7 period (2006-2009) among all age groups, but were only significant among older children. IRs of inpatient ACP decreased across all age groups, but outpatient pneumonia IRs remained stable during the study timeframe, even increasing slightly in children aged 5-17 years. More prominent declines were observed for Medicaid-insured children across all age groups; however, Medicaid IRs were higher than IRs of commercially-insured children during the entire study timeframe. CONCLUSIONS: ACP disease burden remains high in US children of all ages despite overall reductions in incidence rates during 1998-2018 following the introduction of PCV7 and PCV13.