1 Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Kilifi 80108, Kenya. Electronic address: suyoga@kemri-wellcome.org.
2 Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.
3 Medical Research Council Clinical Trials Unit, University College London, London, UK.
4 Department of Infectious Disease, Imperial College, London, UK; Institute of Global Health and Innovation, Faculty of Medicine, Imperial College, London, UK.