Preexposure prophylaxis (PrEP) and postexposure prophylaxis have recently gotten attention as ways to prevent sexually transmitted infections. JAMA Deputy Editor Preeti Malani, MD, MSJ, discusses postexposure prophylaxis using doxycycline (doxyPEP), with Kenneth H. Mayer, MD, professor of medicine and global health at Harvard and medical research director at Fenway Health in Boston.