How PEP Can Prevent HIV After a High-Risk Exposure

Because there is not yet a cure for HIV, or the human immunodeficiency virus, prevention efforts play a key role in managing the HIV/AIDS epidemic. Two major preventative measures for HIV include PrEP (pre-exposure prophylaxis) and PEP (post-exposure prophylaxis).

The difference between PrEP and PEP is somewhat similar to the difference between a standard birth control pill and emergency contraceptive pills (e.g., Plan B). Like a daily birth control pill to prevent pregnancy, PrEP is an oral pill (now also available in a injection every two months) that at-risk individuals take each day to prevent HIV infection. Learn more about what PrEP for HIV is here.

PEP, on the other hand, is an HIV prevention method that you can take after a high-risk exposure to the virus, according to hematologist Jeffrey Laurence, MD, of Weill Cornell Medicine and NewYork-Presbyterian Hospital. Similar to an emergency contraceptive, PEP for HIV must be started within 72 hours after exposure to the virus, whether from a broken condom, unprotected sex, rape, sharing needles, accidental contact with an infected needle, or other forms of contact.

After exposure to HIV, PEP uses antiretroviral medicines to block HIV from permanently infecting the body, says Dr. Laurence. PEP requires taking three medicines (in two tablets) a day for 28 days, and you will need to follow up with your doctor throughout the month to test for HIV and other complications, according to the U.S. Department of Health and Human Services.

If you believe you may have been exposed to HIV, you should call your doctor right away to begin preventive treatment.

However, if you have an ongoing risk of being exposed to HIV, your best option is taking PrEP (pre-exposure) instead of PEP (post-exposure). Find out more about who should take PrEP to prevent HIV.