1. School of Public Health, Department of Epidemiology and Biostatistics, University of Zambia, Lusaka, Zambia
2. Levy Mwanawasa University Teaching Hospital, P. O. Box 810034, Lusaka, Zambia
3. Strategic Centre for Health Systems Metrics & Evaluations (SCHEME), School of Public Health, University of Zambia, Lusaka, Zambia