1. Health Policy Research Center, Mongan Institute, Massachusetts General Hospital, Boston, Massachusetts, USA.
2. Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA.
3. Division of General Internal Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA.
4. Kaiser Permanente Washington, Seattle, Washington, USA.
5. Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, USA.
6. Kaiser Permanente Washington Health Research Institute, Seattle, Washington, USA.
7. Peter O'Donnell Jr. School of Public Health, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
8. Harold C. Simmons Comprehensive Cancer Center, Dallas, Texas, USA.
9. Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
10. Department of Public Health Sciences, University of Chicago Biological Sciences Division, Chicago, Illinois, USA