P-1189. Clinical Characteristics and Outcomes of Medically Attended Respiratory Syncytial Virus (RSV) Infections in Children 24-59 months of Age

Abstract Background RSV infection is a major cause of lower respiratory tract disease (LRTD) among young children. However, clinical features of RSV disease in children ≥24 months of age are not well described. This study assessed the signs, symptoms, and clinical characteristics of RSV in children 24-59 months of age in both outpatient and inpatient settings. Methods We abstracted clinical records from RSV-positive children 24-59 months of age who sought outpatient care for acute respiratory illness (ARI) and who had provided a respiratory swab for RSV testing by RT-PCR as part of influenza vaccine effectiveness studies from 2004-10 and 2014-15. Records were also abstracted for hospitalized children with laboratory-confirmed RSV from 2010-23. We analyzed clinical features of RSV in each care setting. Results We identified 580 pediatric patients 24-59 months with medically attended, laboratory-confirmed RSV infection, including 419 outpatient and 161 inpatient encounters. The prevalence of comorbidities was 31% among outpatients and 66% among inpatients. The median hospital stay was 3.0 days (IQR: 2.0 - 4.3), and 22% were admitted to the pediatric intensive care unit (PICU). Abnormal lung sounds were observed in 21% of outpatients and 70% of hospitalized patients (P< 0.001). Shortness of breath was documented in 6% of outpatients and in 71% of inpatients (P< 0.001). Increased respiratory rate was recorded in 10% of outpatients and in 48% of inpatients (P< 0.001). The median oxygen saturation at the first measurement for outpatients was 96% (IQR: 95%–97%), compared to 93% (IQR: 90%–95%) for inpatients (P < 0.001). In the complete dataset, 25% of outpatients and 93% of hospitalized children aged 24-59 months exhibited signs or symptoms of LRTD, such as retractions, abnormal lung sounds, hypoxemia and/or need for supplemental oxygen. Conclusion Among children 24-59 months of age with medically attended RSV infection, two-thirds of outpatient visits and one-third of inpatient visits occurred in previously healthy children. Nearly one-quarter of hospitalized children required PICU admission, indicating significant morbidity in this age group. Further research on the epidemiology of RSV in children outside of infancy is needed. Disclosures Zhe Zheng, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Jennifer P. King, MPH, GSK Inc.: Grant/Research Support|ModernaTX: Grant/Research Support Linwei Li, n/a, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Tianyu Sun, n/a, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Catherine A. Panozzo, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Thomas G. Boyce, MD, GSK: Grant/Research Support|Moderna, Inc.: Grant/Research Support Iliana Leony Lasso, n/a, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Sabine Schnyder Ghamloush, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Sonia K. Stoszek, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Matthew D. Snape, MBBS, MD, FRCPCH, FPM, FMedSci, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Evan J. Anderson, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Huong McLean, PhD, MPH, CSL Seqirus: Advisor/Consultant|CSL Seqirus: Grant/Research Support|GSK: Grant/Research Support|ModernaTX: Advisor/Consultant|ModernaTX: Grant/Research Support Joshua Petrie, PhD, CSL Seqirus: Grant/Research Support|Moderna, Inc.: Grant/Research Support