1. Department of Paediatrics & Child Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2196, South Africa
2. Centre for HIV & STIs, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg 2131, South Africa
3. Centre for Infectious Disease Epidemiology and Research, University of Cape Town, Cape Town 7925, South Africa
4. National Department of Health, Pretoria 0001, South Africa
5. United Nations Children’s Fund, Pretoria 0011, South Africa