1 Vaccines and Immunity Theme, Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia.
2 The Aurum Institute, Global Health Division, Johannesburg, South Africa.
3 Division of Infectious Diseases and Tropical Medicine, Medical Centre of the University of Munich (LMU) and German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany.
4 Health Economics and Epidemiology Research Office, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.