1. Health Services Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
2. School of Mathematics, University of Nairobi, Nairobi, Kenya
3. Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
4. Institute of Clinical Trials and Methodology, University College London, London, UK
5. Nuffield Department of Medicine, University of Oxford, Oxford, UK
6. Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
7. Mwanza Intervention Trials Unit, Mwanza, Tanzania