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, Johannesburg, South Africa
4. GSK, Wavre, Belgium