RSV Disease Among Hospitalized Children: Second vs. First Year of Life Multicenter Study

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of pediatric hospitalization, yet data on children hospitalized with RSV in their second year of life are limited. OBJECTIVE: To compare clinical characteristics and management practices of children hospitalized with RSV during their second versus first year of life. METHODS: This retrospective multicenter study included children aged 0-23 months hospitalized with RSV infection across 11 medical centers between 2017 and 2021. We compared demographics, outcomes (length of stay [LOS] > 3 days, and pediatric intensive care unit [PICU] admission), and systemic corticosteroid and antibiotic use between the second and first years of life, adjusting for prematurity, comorbidities, and the COVID-19 pandemic. RESULTS: Among 6260 children hospitalized with laboratory-confirmed RSV infection, 1321 (21%) were hospitalized during their second year of life. Compared with first-year admissions, second-year patients had higher rates of prematurity (18.0% vs. 13.4%) and comorbidities (6.3% vs. 2.6%) (both p < 0.001). They more frequently received corticosteroids (53.5% vs. 23.2%) and antibiotics (63.4% vs. 45.9%) (both p < 0.001) and had lower PICU admission rates (4.6% vs. 7.0%; p < 0 0.001) and similar rates of prolonged LOS (35.0% vs. 35.6%; p = 0.64). In adjusted analyses, second-year hospitalization was associated with increased corticosteroid use (adjusted odds ratio [aOR], 4.28; 95% CI, 3.67-4.99) and antibiotic use (aOR, 2.09; 95% CI, 1.80-2.43), and lower odds of PICU admission (aOR, 0.56; 95% CI, 0.40-0.79). CONCLUSIONS: RSV hospitalization in the second year of life carries a significant burden, with higher antibiotic and corticosteroid use despite lower PICU rates and similar LOS. These findings highlight the need for better characterization of this age group to optimize future immunoprophylaxis strategies.