1. Department of Science and Technology/National Research Foundation, Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
2. Respiratory and Meningeal Pathogens Research Unit, Medical Research Council, University of the Witwatersrand, Johannesburg, South Africa
3. Julius Global Health, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands
4. National Institute for Communicable Diseases, Division of National Health Laboratory Service, Centre for Respiratory Diseases and Meningitis, Johannesburg, South Africa
5. Division of Epidemiology and Biostatistics, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
6. Department of Pediatrics, Medicine and Pathology, University of Colorado, Aurora, CO, USA