PrEP is highly effective for preventing HIV.
- PrEP reduces the risk of getting HIV from sex by about 99% when taken as prescribed.
- Although there is less information about how effective PrEP is among people who inject drugs, we do know that PrEP reduces the risk of getting HIV by at least 74% when taken as prescribed.
- PrEP is much less effective when it is not taken as prescribed.
- PrEP reaches maximum protection from HIV for receptive anal sex (bottoming) at about 7 days of daily use.
- For receptive vaginal sex and injection drug use, PrEP reaches maximum protection at about 21 days of daily use.
- No data are available for insertive anal sex (topping) or insertive vaginal sex.
Learn more about the PrEP effectiveness estimate.
Page last reviewed: May 13, 2021