1. Medical Research Council: Respiratory & Meningeal Pathogens Research Unit, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
2. Centre for Vaccines & Immunology, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
3. Department of Science & Technology/National Research Foundation: Vaccine Preventable Diseases, Faculty of Health Sciences, University of the Witwatersrand, South Africa