1. Department of Epidemiology, Colorado School of Public Health, Denver, Colorado, USA
2. Department of Immunology and Microbiology, University of Colorado, Denver, Colorado, USA
3. Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
4. Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, Maryland, USA
5. Department of Health Sciences, University of York, York, United Kingdom