Risk factors associated with severe RSV disease among hospitalized children in the second year of life: a multicenter study.

PURPOSE: The second year of life is gaining increased attention in the era of long-acting RSV immunoprophylaxis. This multicenter study, across pre- and post-COVID seasons, aimed to assess the association between specific key risk-factors and severe RSV-related disease among hospitalized children aged 12-23 months. METHODS: This retrospective study included children aged 12-23 months hospitalized with RSV across 11 medical-centers (2017-2021). We compared outcomes of prolonged hospitalization (> 3 days) and PICU (Pediatric Intensive Care Unit) admission for children with risk factors (prematurity < 37 weeks, major congenital heart disease (CHD), chronic lung disease of prematurity (CLD) or Down syndrome (DS)) and those without the respective risk factor, adjusting for demographic variables and COVID-19 pandemic admission. Clinical outcomes were also compared between children with ≥ 1 risk factors and those with none. RESULTS: Among 1023 children, 228 (22%) had ≥ 1 risk factor: prematurity (n = 183), CLD (n = 28), CHD (n = 45) or DS (n = 20). In multivariable analysis, prematurity with CLD (aOR 4.7,95%CI:1.97-11.22) or without CLD (aOR 2.26, 95%CI:1.54-3.3), CHD (aOR-3.29, 95%CI:1.6-6.77), DS (aOR-4.14, 95%CI:1.26-13.6) and having ≥ 1 risk (aOR-3.55, 95%CI:2.55-4.96) were independently associated with prolonged hospitalization. DS (aOR 6.7, 95%CI:2.1-22.4), CHD (aOR 3.0,95%CI:1.04-8.66) and having ≥ 1 risk factor (aOR-3.58, 95%CI:1.89-6.80) were also associated with PICU admission. CONCLUSION: Children aged 12-23 months with prematurity, CLD, major CHD or DS had significantly higher rates of prolonged RSV hospitalization. Those with ≥ 1 risk factor, and presumably patients with DS and CHD are at highest risk for severe complications. Preventive strategies for these high-risk populations should be considered in their second-year of life. WHAT IS KNOWN: • Children with prematurity, congenital heart disease (CHD), chronic lung disease of prematurity (CLD) or Down syndrome (DS) are at increased risk for severe RSV-related illness in the first year of life. • The second year of life is now relevant for long-acting RSV prevention strategies. WHAT IS NEW: • This multicenter study shows that prematurity, CLD, CHD, and DS remain strong predictors of prolonged RSV hospitalization in children aged 12-23 months. • Those with ≥ 1 risk factor, and presumably those with DS and major CHD, faced the highest risk, with increased likelihood of PICU admission.