Cohort characteristics
Demographic (age, gender), and clinical characteristics (underlying disease) of recorded cases by PHO unit and location in a pediatric or general hospital are shown in Table 1 . Patients hospitalized in PHO units located in general hospitals were significantly younger than patients hospitalized in PHO units located in pediatric hospitals [(pediatric hospitals: median 7.5 years (IQR 3.6-12.3) versus general hospitals: median 5.4 years (IQR 3.1-8.5), p =0.001]. In addition, significantly more female patients were hospitalized in PHO units located in general hospitals.