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How Effective is Post-Exposure Prophylaxis (PEP) ?


Hi, I had unprotected sex with a lady, two weeks later we tested for hiv and hers came out positive and mine negative, I then immediately began PEP treatment, will this treatment ensure i remain negative? Could i infect someone else with HIV if i had unprotected sex three days after the exposure?



Thank you for your inquiry. From what we gather from the question, you were asking about the effectiveness of Post-exposure prophylaxis (PEP).

If PEP is started within 72 hours of exposure, it can decrease the risk of acquiring HIV by approximately 80%. [1] In addition, using condoms can also decrease the risk of acquiring HIV by 80% or more. [2].


  1. http://www.cfenet.ubc.ca/sites/default/files/uploads/publications/centredocs/pep_guidelines_07-jun-2018.pdf
  2. Weller, Susan C., and Karen Davis‐Beaty. "Condom effectiveness in reducing heterosexual HIV transmission." The Cochrane Library (2002).

Regards, AIDS Vancouver Helpline/Online, Ashley