1. Department of Clinical Epidemiology, Institute of Infectious Disease and Epidemiology, Tan Tock Seng Hospital, Singapore
2. Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, United States
3. Department of Infectious Diseases, Institute of Infectious Disease and Epidemiology, Tan Tock Seng Hospital, Singapore
4. Yong Loo Lin School of Medicine, National University of Singapore, Singapore
5. Center for Health Policy Research, University of California, Los Angeles (UCLA), Los Angeles, United States