1. Clinical Trial Service Unit and Epidemiological Studies Unit, Nuffield Department of Population Health, University of Oxford, Oxford, England
2. Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China3Chinese Academy of Medical Sciences, Beijing, China
3. Chinese Academy of Medical Sciences, Beijing, China
4. China National Center for Food Safety Risk Assessment, Beijing, China
5. Henan Centre for Disease Control and Prevention, Zhengzhou, China
6. Heilongjiang Centre for Disease Control and Prevention, Harbin, China
7. Hainan Centre for Disease Control and Prevention, Haikou, China
8. Liuzhou Centre for Disease Control and Prevention, Liuzhou, China
9. Tongxiang Centre for Disease Control and Prevention, Tongxiang, China