1. Department of Biostatistics University of Washington Seattle Washington USA
2. Biostatistics, Bioinformatics and Epidemiology Program Fred Hutchinson Cancer Center Seattle Washington USA
3. Public Health Sciences Division Fred Hutchinson Cancer Center Seattle Washington USA
4. Department of Infectious Disease Epidemiology London School of Hygiene and Tropical Medicine London England UK
5. School of Medicine Johns Hopkins University Baltimore Maryland USA
6. Division of Intramural Research National Institute of Allergy and Infectious Diseases Baltimore Maryland USA