1 KEMRI-Wellcome Trust Research Programme, Health Services Research Group, Nairobi, Kenya; Department of Global Health, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands. Electronic address: mmaina@kemri-wellcome.org.
2 University of Oxford, Nuffield Department of Medicine, Oxford, UK.
3 KEMRI-Wellcome Trust Research Programme, Health Services Research Group, Nairobi, Kenya; University of Oxford, Nuffield Department of Medicine, Oxford, UK.
4 Department of Global Health, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands; Amsterdam Institute for Global Health and Development, Amsterdam, Netherlands.