PEP (post-exposure prophylaxis) is a 28 day course of HIV drugs that someone takes very soon after sex to reduce their chances of becoming infected with HIV.

The sooner PEP is started, the more likely it is to work; within 24 hours is best, but no later than 72 hours. After 72 hours PEP is unlikely to work.

 

What are the risks of someone getting HIV after sex without PEP?

This depends on the type of sexual intercourse, the HIV viral load in the index partner and the susceptibility of the recipient if the index partner is not virologically suppressed.