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