1. Department of Preventive Medicine, College of Medicine, Seoul National University, Korea.
2. Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.
3. Division of Vaccine Preventable Disease Control and National Immunization Program, Korean Centers for Disease Control and Prevention, Korea.
4. Department of Pediatrics, Seoul National University Children's Hospital, Korea.
5. Department of Pediatrics, Inje University Haeundae Paik Hospital, Korea.