Nathan K. Cobb is with the Department of Pulmonary and Critical Care, Georgetown University Medical Center, Washington, DC, and the Department of Health, Behavior and Society, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD. Megan A. Jacobs is with the Schroeder Institute for Tobacco Research and Policy Studies, Truth Initiative, Washington, DC. Paul Wileyto is with the Department of Biostatistics & Epidemiology, University of Pennsylvania School of Medicine, Philadelphia. Thomas Valente...