1. School of Public Health, University of the Western Cape, Robert Sobukwe Road, Bellville, Cape Town, South Africa
2. Health Policy and Systems Division, School of Public Health and Family Medicine, University of Cape Town, Anzio Road, Observatory, Cape Town, South Africa
3. Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA
4. Queen Mary University of London, 58 Turner Street, London
5. Department of Global Health and Development, London School of Hygiene and Tropical Medicine, Keppel Street, London, UK