1 Health Services Unit, Kenya Medical Research Institute-Wellcome Programme, Nairobi, Kenya; Health Systems Collaborative, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7BN, UK. Electronic address: mike.english@ndm.ox.ac.uk.
2 Centre for Health Policy and South African Research Chairs Initiative, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
3 School of Public Health, Makerere University, Kampala, Uganda.
4 Faculty of Public Health and Policy, London School of Hygiene & Tropical Medicine, London, UK.