1. Division of Infectious Diseases, Department of Medicine and Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
2. Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
3. Department of Pediatrics and Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
4. Department of Medicine and Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
5. Vaccine Research Laboratory, University of British Columbia Centre for Disease Control, Vancouver, Canada