Objective: To synthesize existing evidence on the risk factors, preventive measures, and long-term outcomes of lower respiratory tract infections (LRTIs) in early childhood, and to identify key gaps in research and policy.
Methods: A systematic search was conducted in PubMed, Scopus, and Web of Science for studies published between January 2000 and August 2025, supplemented by reports from WHO, UNICEF, and the Global Burden of Disease (GBD) database. Eligible studies included randomized controlled trials, cohort, case-control, and cross-sectional studies, as well as systematic reviews involving children aged 0-5 years. Studies focused solely on acute treatment or adult populations were excluded.
Results: Early-life LRTIs arise from interacting determinants, including prematurity, malnutrition, indoor air pollution, inadequate immunization, and socioeconomic inequities. Preventive strategies such as vaccination, maternal immunization, exclusive breastfeeding, micronutrient supplementation, and the use of clean fuels-significantly reduce childhood morbidity and mortality. Evidence also indicates long-term health consequences, including asthma, impaired lung function, neurodevelopmental delay, and increased cardiometabolic risk.
Conclusions: Early-life LRTIs represent both an acute health burden and a determinant of lifelong respiratory and systemic outcomes. Expanding equitable vaccination coverage, improving maternal and child nutrition, reducing environmental exposures, and strengthening health-system capacity are essential to mitigate both short- and long-term global impacts.
Keywords: Lower respiratory tract infections; RSV; bronchiolitis; global health; maternal and neonatal interventions; pneumonia; vaccines.