A 21-year-old cisgender woman is evaluated in the emergency room after reporting she was sexually assaulted by a single male assailant. The accused male assailant is arrested and agrees to laboratory testing. The female assault survivor has never received the hepatitis B vaccine. Empiric treatment for sexually transmitted infections is given, laboratory tests are ordered, and HIV postexposure prophylaxis is started. After 24 hours, the laboratory test results for the sexual assault survivor and assailant become available; based on these results the HIV postexposure prophylaxis (PEP) is discontinued. The results are shown below (Table 1).