No. PrEP (Pre-Exposure Prophylaxis) can only prevent HIV when taken consistently BEFORE exposure. PrEP cannot be started as a method of treatment AFTER an event of HIV exposure (such as sex without a condom, needle-sharing drug use, or sexual assault). PEP (Post-Exposure Prophylaxis) is the 28-day treatment regimen recommended for people who’ve been exposed to HIV. If you think you have been exposed to HIV, it is important that you start taking PEP as soon as possible. PEP is only effective if taken within 72 hours of possible HIV exposure. If you are exposed to HIV during a weekend, or you cannot make an appointment for the next day with your primary care doctor, go to an emergency room for immediate treatment. Do not wait more than 36 hours to start PEP treatment. If you are currently taking PEP, talk to your doctor before starting PrEP. Blood testing and a short wait time are required to make sure you are HIV-negative after finishing a PEP regimen.