1. Center for Clinical Epidemiology and Evidence-based Medicine, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
2. Department of Epidemiology and Biostatistics, School of Public Health, Capital Medical University, Beijing, China
3. Clinical Research Unit, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
4. Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
5. Children’s Hospital of Eastern Ontario Research Institute,Department of Pediatrics and School of Epidemiology and Public Health, University of Ottawa, Ottawa, Canada
6. Institute for Clinical Evaluative Sciences, Toronto, Canada
7. Key Laboratory of Major Diseases in Children, Ministry of Education, Beijing, China