1. University of California, San Francisco, California, USA
2. The George Washington University Biostatistics Center, Rockville, Maryland, USA
3. Duke University, Durham, North Carolina, USA
4. Alameda County Department of Public Health, Oakland, California, USA
5. Durham Veterans Affairs Health Care System, Durham, North Carolina, USA
6. National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
7. Mayo Clinic, Rochester, Minnesota, USA
8. University of California, Los Angeles, California, USA