1497 - Epidemiology of RSV infection in Japan: A nationwide claims database analysis

Background: Respiratory syncytial virus (RSV) is the major global cause of hospitalization for bronchiolitis and pneumonia in infancy around the globe. In Japan, the occurrence of RSV infection is monitored under the national pediatric sentinel surveillance system. However, this system does not provide detailed information about patient distribution by month of birth and clinical features. We aimed to describe the national epidemiology and clinical features of RSV infection in children < 24 months of age utilizing a nationwide healthcare claims database in Japan.

Methods: We retrospectively analysed anonymized claims data from the Japan Medical Data Center (JMDC) of medical insurance beneficiaries who had at least one confirmed RSV-related diagnosis by ICD10 codes between January 2017 and December 2018. In children < 24 months of age, the number of patients by age in Japan was estimated using the prevalence of patients in the database and national population data by age.

Results: In the JMDC database, 9,711 and 8,509 children < 24 months of age had an RSV-related diagnosis in 2017 and 2018, respectively. Of which, 2,473 (25%) and 2,083 (24%) were hospitalized. When extrapolated to the entire Japanese population, an estimated 138,059 and 119,205 RSV-related diagnoses and 33,355 and 27,339 RSV-associated hospitalizations occurred in Japan in 2017 and 2018, respectively. Infants < 6 months of age accounted for between 39% and 42% of total hospitalisations for RSV. A peak in RSV hospitalization was observed at age 2 months. Only 10% of all children < 24 months of age who were hospitalised with an RSV infection had a specific underlying medical condition (preterm infant, bronchopulmonary dysplasia, Down syndrome, chronic heart disease, immunodeficiency). The estimated rate of RSV-associated hospitalization was 35.4 per 1000 population per year among infants < 6 months of age.

Conclusion: In conclusion, 3 to 4 out of every 100 Japanese children aged < 6 months were hospitalized for RSV. Ninety percent of children < 24 months of age hospitalised with RSV infection did not have a recognised underlying medical condition. The peak of hospitalization for RSV infection occurred at 2 months of age. Thus, broad-based prevention strategies targeting young infants are needed.