1. Public Health Research Institute, National Medical Center, Seoul, Korea.
2. Department of Pediatrics, National Medical Center, Seoul, Korea.
3. Department of Pediatrics, Seoul National University Hospital, Seoul, Korea.
4. Department of Preventive Medicine, Konkuk University College of Medicine, Chungju, Korea.
5. National Emergency Medical Center, National Medical Center, Seoul, Korea.
6. Department of Population Health, NYU Grossman School of Medicine, New York, NY, USA.
7. Center for Public Health Data Analytics, National Medical Center, Seoul, Korea.