PEP is short for Post Exposure Prophylaxis. It reduces the chance of HIV infecting your body after you’ve been exposed to it. You take it AFTER sex and it is recommended when the risk of catching HIV is over 1 in 1,000. Check your risk here.
Ideally it should be started within 24 hours. The treatment lasts for 28 days. A&E departments are able to start PEP when the clinic is closed. It’s thought that PEP reduces the chance of HIV infection by at least 80%.