1. Department of Epidemiology and Medical Statistics, College of Medicine, University of Ibadan, Ibadan, Nigeria
2. Demography and Population Studies, Schools of Public Health and Social Sciences, University of the Witwatersrand, Johannesburg, South Africa
3. Infectious Disease Institute, College of Medicine, University of Ibadan, Ibadan, Nigeria
4. Department of Obstetrics and Gynaecology, College of Medicine, University of Ibadan, Ibadan, Nigeria