(A29) Natural History of RSV Infection in Outpatient Pediatric Patients in the United States

Publication Number: 312

Background: Respiratory syncytial virus (RSV) infection is nearly ubiquitous during the first two years of life, and those at the youngest ages and with high-risk conditions (preterm, congenital heart disease, chronic lung disease, immunocompromised) are at an increased risk for severe lower respiratory tract infection (LRTI) or hospitalization. Most are managed successfully at home, yet data is sparse on the natural history of the infection in non-hospitalized children. Elucidation of disease course, including healthcare utilization, symptoms, and progression to LRTI in the outpatient setting would inform clinical trial design for antiviral drugs to treat subjects at risk of severe RSV.

Objectives: To characterize the natural history of RSV infection in non-hospitalized children ( < 5 years) who tested positive in the outpatient setting.

Methods: In the US-based Optum, de-identified integrated electronic health records (EHR) with claims database, children with a positive RSV laboratory test (quantitative real-time polymerase chain reaction or antigen) in the ambulatory setting (emergency department (ED), office/clinic, or urgent care) were identified between October 2016 and December 2019. All analyses were stratified by age (0 to < 2 years, 2 to < 5 years). Diagnoses at index (date of RSV positive test) and follow-up healthcare encounters were captured using ICD-10 codes; LRTI was defined as the presence of pneumonia or bronchiolitis. Healthcare utilization outcomes were assessed 4, 6, and 14 days after index.

Results: From 2016-2019, 44,947 children < 2 and 10,400 2 to < 5 years tested positive for RSV in the ambulatory setting within the Optum database. The majority were diagnosed in the ED (39%) or primary care office (28%), while 22% were diagnosed in urgent care/ambulatory services, and 4% in an observation ( < 24 hours) setting. Acute bronchiolitis due to RSV and cough were the most common initial diagnoses. Among children < 2 years, 61.7% had at least one follow-up healthcare encounter in the 14 days following test, with 41.1% presenting with LRTI at their second visit. Within 4 days of index, 3.1% of children < 2 years were admitted to the hospital and 9.6% sought acute ambulatory care (ED, urgent care, or observation < 24 hours); within 14 days of follow-up, these figures rose to 3.3% and 11.1%, respectively. Fewer children (49.7%) 2 to < 5 years had any follow-up healthcare encounter(s) in 14 days of follow-up.

Conclusions: A substantial portion of outpatient children < 2 years with RSV progressed to LRTI, while hospitalization remained relatively uncommon. Further analyses of other real-world databases are needed to evaluate the natural history of RSV infection in outpatient pediatric patients in the US and globally.