1 Polio Eradication Programme and Vaccine-Preventable Diseases Programme, WHO Regional Office for Africa, Brazzaville, Republic of the Congo. Electronic address: [email protected].
2 Cochrane South Africa, South African Medical Research Council, Cape Town, South Africa.
3 Department of Community Medicine, Bayero University and Aminu Kano Teaching Hospital, Kano, Nigeria.
4 Polio Eradication Programme and Vaccine-Preventable Diseases Programme, WHO Regional Office for Africa, Brazzaville, Republic of the Congo.
5 Polio Eradication Programme and Vaccine-Preventable Diseases Programme, WHO Regional Office for Africa, Brazzaville, Republic of the Congo; Cochrane South Africa, South African Medical Research Council, Cape Town, South Africa; Division of Epidemiology and Biostatistics, Department of Global Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.