1 Medical Research Council Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK.
2 Centre for Mathematical Modeling of Infectious Diseases, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK.
3 Bill & Melinda Gates Foundation, Seattle, WA, USA.
4 Bill & Melinda Gates Foundation, Seattle, WA, USA. supriya.kumar@gatesfoundation.org.