1. Department of Epidemiology and Biostatistics, School of Public Health, Peking University, No. 38, Xueyuan Road, Haidian District, Beijing 100191, China
2. Institute for Global Health and Development, Peking University, No. 5, Yiheyuan Road, Haidian District, Beijing 100871, China
3. Department of Global Health and Population, Harvard TH Chan School of Public Health, 677 Huntington Avenue Boston, Boston, MA 02115, USA