Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, USA; Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA; Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA; Madigan Army Medical Center, Joint Base Lewis McChord, Washington, USA