1. Department of Epidemiology & Biostatistics, School of Public Health, Peking University, Beijing 100191, PR China
2. Department of Medical Epidemiology & Biostatistics, Karolinska Institute, 171 76 Stockholm, Sweden
3. Qingdao Center for Disease Control & Prevention, Qingdao 266033, PR China
4. Zhejiang Center for Disease Control & Prevention, Hangzhou 310051, PR China
5. Jiangsu Center for Disease Control & Prevention, Nanjing 210009, PR China
6. Sichuan Center for Disease Control & Prevention, Chengdu 610041, PR China