1. Division of Infectious Diseases, Department of Medicine Perelman School of Medicine at the University of Pennsylvania Philadelphia PA USA
2. GlaxoSmithKline Rockville MD USA
3. Center for Clinical Epidemiology and Biostatistics Perelman School of Medicine at the University of Pennsylvania Philadelphia PA USA
4. Department of Biostatistics, Epidemiology, and Informatics Perelman School of Medicine at the University of Pennsylvania Philadelphia PA USA
5. Division of Infectious Diseases, Department of Pediatrics The Johns Hopkins University School of Medicine Baltimore MD USA
6. Department of Epidemiology and Public Health University of Maryland School of Medicine Baltimore MD USA
7. Division of Infectious Diseases, Department of Medicine University of Maryland School of Medicine Baltimore MD USA
8. Department of Pathology and Laboratory Medicine University of North Carolina School of Medicine Chapel Hill NC USA