1. Internal Medicine C, Sheba Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Israel
2. Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
3. Healthcare Cost and Utilization Project, Center for Delivery, Organization and Markets, Agency for Healthcare Research and Quality, Rockville, Maryland
4. Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia