Conflict of Interest and Sources of Funding: J.S. is a member of Merck KGaA's Ethics Advisory Panel and Stem Cell Research Oversight Committee, a member of IQVIA's Ethics Advisory Panel, and a member of Aspen Neurosciences' Clinical Advisory Panel He was previously a member of a Merck Data Monitoring Committee and a consultant to Biogen. None of these activities are related to the material discussed in this manuscript. Fenway Health is a subrecipient of a grant to Mpact: Global Action for Gay Men's Health and Rights from Glaxo Smith Kline for a research project on knowledge of and attitudes toward hepatitis A and B vaccination among gay and bisexual men and transgender people in the United States and Mexico. S.C. is the principal investigator of this project. S.C. is on the Patient Advocate Steering Committee for Prostate Cancer Clinical Trials for Janssen Global Services representing gay and bisexual men and transgender women. None of these activities are related to the material discussed in this article. C.C. has served as an advisory board member to Gilead Sciences, Merck, and Viiv and an expert witness for Gilead Sciences. None of these activities are related to the material discussed in this article. Stephanie E. Cohen has received laboratory support from Cepheid and Hologic and medication donation from Mayne Pharma, to support the conduct of the DoxyPEP study. A.F.L. has received laboratory support from Cepheid and Hologic and medication donation from Mayne Pharma, to support the conduct of the DoxyPEP study. She has received grant support from Gilead, Merck, and Viiv to UCSF, unrelated to this work. Fenway Health is the recipient of funding from the Centers for Disease Control and Prevention through a subcontract with National Association of County and City Health Officials to assess the roll-out of DoxyPEP. K.H.M. is the subcontract principal investigator. Fenway Health has also received unrestricted research grants from Gilead Sciences and Merck, Inc., and K.H.M. is the principal investigator for those grants. K.H.M. is on scientific advisory boards for Gilead Sciences and Merck, Inc., focusing on HIV prevention. H.A.T.'s effort is funded by the National Institutes of Health Clinical Center, Department of Bioethics.