ABSTRACT
BACKGROUND: Childhood lower respiratory tract infections (LRTIs) cause substantial morbidity and under-5 child mortality. The epidemiology of LRTI is changing in low- and middle-income countries with expanding access to conjugate vaccines, yet there are few data on the incidence and risk factors for LRTI in these settings. METHODS: A prospective birth cohort enrolled mother-infant pairs in 2 communities near Cape Town, South Africa. Active surveillance for LRTI was performed for the first 2 years of life over 4 respiratory seasons. Comprehensive data collection of risk factors was done through 2 years of life. World Health Organization definitions were used to classify clinical LRTI and chest radiographs. RESULTS: From March 2012 to February 2017, 1143 children were enrolled and followed until 2 years of age. Thirty-two percent of children were exposed to antenatal maternal smoking; 15% were born at low birth weights. Seven hundred ninety-five LRTI events occurred in 429 children by February 2017; incidence of LRTI was 0.51 and 0.25 episodes per child-year in the first and second years of life, respectively. Human immunodeficiency virus (HIV)-exposed, uninfected infants (vs HIV-unexposed infants) were at increased risk of hospitalized LRTI in the first 6 months of life. In regression models, male sex, low birth weight, and maternal smoking were independent risk factors for both ambulatory and hospitalized LRTI; delayed or incomplete vaccination was associated with hospitalized LRTI. CONCLUSIONS: LRTI incidence was high in the first year of life, with substantial morbidity. Strategies to ameliorate harmful exposures are needed to reduce LRTI burden in vulnerable populations.