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  • Dr Jonathan Gui

HIV Prevention (PEP - Post Exposure Prophylaxis)

Updated: Jun 9, 2019


PEP stands for post-exposure prophylaxis. It means taking antiretroviral medicines (ART) after being potentially exposed to HIV to prevent becoming infected.

PEP must be started within 72 hours after a recent possible exposure to HIV, but the sooner you start PEP, the better. Every hour counts. If you’re prescribed PEP, you’ll need to take it once or twice daily for 28 days. PEP is effective in preventing HIV when administered correctly, but not 100%.

If you’re HIV-negative or don’t know your HIV status, and in the last 72 hours you

think you may have been exposed to HIV during sex (for example, if the condom broke),shared needles and works to prepare drugs (for example, cotton, cookers, water), or were sexually assaulted, talk to your health care provider or an emergency room doctor about PEP right away.

PEP should be used only in emergency situations and must be started within 72 hours after a recent possible exposure to HIV. It is not a substitute for regular use of other proven HIV prevention methods, such as pre-exposure prophylaxis (PrEP), which means taking HIV medicines daily to lower your chance of getting infected; using condoms the right way every time you have sex; and using only your own new, sterile needles and works every time you inject.


PEP is effective, but not 100%, so you should continue to use condoms with sex partners and safe injection practices while taking PEP. These strategies can protect you from being exposed to HIV again and reduce the chances of transmitting HIV to others if you do become infected while you’re on PEP.

If you’re a health care worker and think you’ve had a possible HIV exposure at work, see the following question.


Learn more about how to protect yourself and get information tailored to meet your needs from CDC’s HIV Risk Reduction Tool (BETA).


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