[1] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, 16 Med Dr, Singapore 117597, Singapore
[2] Harvard Univ TH Chan Sch Publ Hlth, Boston, MA USA
[3] Univ Calif San Francisco, EPPIctr Program, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA
[5] Univ Oxford, Clin Res Unit Vietnam, Ho Chi Minh City, Vietnam
[6] Univ Florida, Dept Biol, Gainesville, FL USA
[7] Princeton Univ, Princeton, NJ 08544 USA
[8] Univ Cambridge, Cambridge, England
[9] London Sch Hyg & Trop Med, London, England