Risk factors for respiratory syncytial virus-associated acute lower respiratory infection in children under 5 years: An updated systematic review and meta-analysis.

Objectives: Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection (ALRI) in young children. With substantial advances in RSV research, we aimed to conduct an updated systematic review of risk factors for RSV-ALRI in children under 5 years.

Methods: We updated our previously published literature search to November 2022 among three English databases and additionally searched three Chinese databases (from January 1995) to identify all relevant publications. We performed random-effects meta-analyses to estimate the pooled odds ratio (OR) and 95% confidence interval (CI) for each risk factor and each outcome (RSV-ALRI in the community and RSV-ALRI hospitalization).

Results: A total of 47 studies were included (26 from the updated search). Indoor air pollution was identified as a possible risk factor for RSV-ALRI in the community (OR 1.45, 95% CI: 1.10-1.90). The identified risk factors for RSV-ALRI hospitalization fall into four categories: demographic (male sex, Māori and Pacific ethnicities vs European or other ethnicities), pre- and post-neonatal (prematurity, low birth weight, small for gestational age, maternal smoking during pregnancy or lactation, maternal age <30 years vs 30-34 years, multiparity, caesarean section vs vaginal), household and environmental (having siblings, passive smoking, maternal asthma, daycare centre attendance) and health and medical conditions (any chronic diseases, bronchopulmonary dysplasia, HIV infections, congenital heart disease, Down syndrome, cystic fibrosis, previous asthma). The pooled ORs ranged from 1.14 to 4.55.

Conclusion: Our findings on the risk factors for RSV-ALRI help identify RSV high-risk groups, which has important implications for RSV prevention at both individual and population levels.