PrEP Effectiveness

Q: How long do I have to take PrEP before it is highly effective?

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 .

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How effective is PrEP?

Learn about your HIV risk and how to lower it.

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.

How long do I have to take PrEP before it is highly effective?

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.