[1] Univ Stellenbosch, Fac Med & Hlth Sci, Dept Interdisciplinary Hlth Sci, Biostat Unit,Ctr Evidence Based Hlth Care, ZA-8000 Cape Town, South Africa
[2] Univ Stellenbosch, Ctr Evidence Based Hlth Care, Dept Interdisciplinary Hlth Sci, ZA-8000 Cape Town, South Africa
[3] Univ Zimbabwe, Dept Community Med, Harare, Zimbabwe
[4] Univ Zambia, Dept Publ Hlth, Lusaka, Zambia
[5] Univ KwaZulu Natal, Sch Nursing & Publ Hlth, Discipline Publ Hlth Med, Durban, South Africa
[6] London Sch Hyg & Trop Med, Dept Populat Hlth, London WC1, England
[7] Univ Oxford, Nuffield Dept Clin Med, Oxford, England
[8] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada
[9] Univ Stellenbosch, Dept Interdisciplinary Hlth Sci, ZA-8000 Cape Town, South Africa