1. Institute of Social & Preventive Medicine University of Bern Bern Switzerland
2. Empilweni Services and Research Unit Department of Paediatrics & Child Health Rahima Moosa Mother and Child Hospital Faculty of Health Sciences University of the Witwatersrand Johannesburg South Africa
3. Wits Reproductive Health and HIV Institute Faculty of Health Sciences University of the Witwatersrand Johannesburg South Africa
4. Centre for Infectious Disease Epidemiology and Research University of Cape Town Cape Town South Africa
5. Population Health Sciences Bristol Medical School University of Bristol Bristol United Kingdom