1 Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK. Electronic address: matthew.chico@lshtm.ac.uk.
2 Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
3 London, United Kingdom.
4 Avenir Health, Geneva, Switzerland.
5 Faculty of Infectious and Tropical Diseases, and Department of Medical Statistics, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK.
6 Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK.
7 Centers for Disease Control and Prevention, Division of STD Prevention, Atlanta, GA, USA.