1. Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center , Seattle, WA 98109 , USA
2. Department of Applied Mathematics, University of Washington , Seattle, WA 98195 , USA
3. Infectious Economics , New York, NY 10025 , USA
4. Comparative Health Outcomes, Policy and Economics (CHOICE) Institute, School of Pharmacy, University of Washington , Seattle, WA 98195 , USA