1. Graduate Group of Applied Mathematics and Computational Science, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA;
2. Department of Biostatistics, School of Global Public Health, New York University, New York City, NY;
3. Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA;
4. Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, Seattle, WA