Factors associated with severe pneumonia among hospitalised children under five years of age: a cross-sectional study at Hai Duong Children's Hospital, Hai Duong, Vietnam

Introduction: severe pneumonia remains a major contributor to morbidity and mortality among children under five years of age in low- and middle-income countries. Evidence on factors independently associated with severe pediatric pneumonia in Vietnam is limited. This study aimed to determine the rate of severe pneumonia and identify factors independently associated with disease severity among children aged 2-59 months hospitalised with community-acquired pneumonia at Hai Duong Children's Hospital, Hai Duong, Vietnam. Methods: a hospital-based cross-sectional study was conducted among children aged 2-59 months admitted with community-acquired pneumonia to Hai Duong Children's Hospital, Hai Duong, Vietnam, from November 2024 to April 2025. Data on demographic characteristics, perinatal history, vaccination status, underlying diseases, nutritional status, caregiver education, and duration of illness before admission were collected prospectively. Pneumonia severity was classified according to Vietnamese Ministry of Health 2014 guidelines. Multivariable logistic regression analysis was performed to identify factors independently associated with severe pneumonia, and adjusted odds ratios (aOR), 95% confidence intervals (CI), and p values were reported. Results: among 570 hospitalised children aged 2-59 months, 319/570 (56.0%) were male and 313/570 (54.9%) were aged 12-<60 months. Overall, 167/570 children (29.3%) were classified as having severe pneumonia. In multivariable logistic regression analysis, preterm birth was independently associated with severe pneumonia (aOR: 2.32, 95% CI 1.08-4.95; P=.030). Underlying diseases were also associated with increased odds of severe pneumonia (aOR: 2.83, 95% CI 1.62-4.94; P<.001). Children not vaccinated with the 5-in-1 or 6-in-1 vaccine had higher odds of severe pneumonia (aOR: 2.68, 95% CI 1.20-5.95; P=.016), as did those without pneumococcal vaccination (aOR: 1.78, 95% CI 1.12-2.84; P=.015). In addition, caregiver education below high school level was independently associated with severe pneumonia (aOR: 2.45, 95% CI 1.34-4.49; P=0.004). Conclusion: in this hospital-based study at Hai Duong Children's Hospital, severe pneumonia accounted for 29.3% of pediatric pneumonia admissions. Preterm birth, underlying diseases, incomplete routine and pneumococcal vaccination, and lower caregiver educational level were independently associated with severe pneumonia in this study population.