1. Cochrane South Africa, South African Medical Research Council, Cape Town, South Africa
2. Division of Epidemiology and Biostatistics, Department of Global Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
3. Department of Community Medicine, Bayero University/Aminu Kano Teaching Hospital, Kano, Nigeria
4. Vaccine-Preventable Diseases Programme, World Health Organization Regional Office for Africa, Brazzaville, Congo