Pre-exposure prophylaxis, or PrEP, is a way for people who do not have HIV but who are at substantial risk of getting it to prevent HIV infection by taking a pill every day. When someone is exposed to HIV through sex or injection drug use, PrEP can work to keep the virus from establishing a permanent infection.

When taken as prescribed, PrEP blocks HIV from taking hold in the body. Daily PrEP use can lower the risk of HIV by an estimated 99 percent. Another study focusing on sex between men and women showed PrEP reduced the risk of getting HIV by at least 90 percent. PrEP is much less effective if it is not taken consistently.

PrEP is a powerful HIV prevention tool and can be combined with condoms and other prevention methods to provide even greater protection than when used alone. But people who use PrEP must commit to taking the drug every day and seeing their health care provider for follow-up every 3 months.