1 Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya; Department of Paediatrics and Child Health, College of Health Sciences, University of Nairobi, Nairobi, Kenya. Electronic address: jaluvaala@kemri-wellcome.org.
2 Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya; Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.