Question
Is PEP effective if taken 48 hours after exposure?
2 July 2021. Related: All topics, PEP/PEPSE.
I paid for sex with a woman but the condom tore and I only realised after I was done. There is a high chance that she was HIV positive. I started PEP after 48 hours.
I got a PCR test done 17 days after exposure. It had a less than 20/ml (undetectable) result.
Now between 14 and 35 days after exposure I have had signs of thrush, mild red rash on my face and a couple elsewhere. But no fever or swollen lymph glands.
Can the rash and thrush be because of utter stress and obsession?
My doctor says that the PCR can be relied upon and that I am negative.
Can the PEP have reduced the viral load to less than 20/ml as I took it for 15 days before the PCR test?
Please give your expert advice. I am very anxious. Thank you.
Answer
Thank you for your question.
The risk of HIV from one broken condom is very low. If your partner had an undetectable viral load on treatment, then the risk would be zero. If they were not on treatment the risk might still be only 1 in 300 or lower.
You cannot guess someones HIV status so your assumptions might also be wrong.
You started PEP within 48 hours, so it is likely it will work.
PEP – stands for Post-Exposure Prophylaxis. It is a term used for taking HIV drugs to reduce the risk of infection. PEP usually involves taking a combination of three HIV drugs for one month. The earlier PEP is started, the more likely it will work. Ideally, this should be within a couple of hours. If this is not possible, then still the earlier the better.
Some guidelines include a two-day window to do this (i.e. within 48 hours). After this, effectiveness is much less likely. Other guidelines allow up to 3 days (i.e. within 72 hours). Sometimes this may be more for psychological benefit. For example, if someone is very stressed or traumatised.
No guidelines recommend starting PEP after 72 hours.
After finishing PEP you need to wait a 4-6 weeks before testing.
If the PEP has worked, or the person was not initially infected, this will show as a negative HIV test. The test you did 17 days after the exposure will not be accurate yet.
If the PEP has not worked, this will be shown in a positive test result. Testing 4 weeks after PEP will detect 95% of infections. Testing after six weeks will detect more than 99% of infections. This result doesn’t need to be tested again.
If PEP has not worked, serosonversion usually occurs 1-3 weeks after PEP is finished. However, only 80% of people show symptoms.
Please test 6 weeks after you finished PEP is finished. If you test any earlier, you need to take a second test 3 months later.
Viral load (PRC) tests are not approved to test for HIV. In some cases they can have a role.
Please see a doctor to talk about your symptoms he best way to confirm what is causing them is to see your doctor. He/she will be able to diagnose and treat the symptoms accordingly.
Note: This answer was last updated in July 2021 from an original post from December 2011.
Hi Dewey, this will not lower the effectiveness of PEP. AS you still started the full dose within 72 hours PEP will still be effective.
For transmission risk please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
After a possible exposure, I went to the ER and got the first half dose of PEP 9 hours after the incident. Due to some issues, the pharmacy wasn’t able to give me the second of half of the PEP dose within 24hrs. So I received my first full dose 40 hours after the incident. Does this lower the effectiveness of PEP and what are the chances of getting infected by HIV on my first time having unprotected intercourse?
Hi John, a test is conclusive 6 weeks after the last dose of PEP. This will be using a 4th generation test.
For more information please see here: https://i-base.info/qa/factsheets/pep-faq
I had unprotected sex with an hiv-positive and I started pep after 9 day’s after finishing my pep i test negative at 40day’s of exposure with 4th generation . How accurate is the test
Hi Turk, as you have started PEP within a suitable time window this is all you need to do. Continue with your course of PEP at the same time each day for the for the 28 day duration of the course.
Are you able to have the blood from the needle/previous patient tested?
Hey, good afternoon
At 25/08/2023(time 1:00pm)
I was working in my lab and I got injured by a needle ( which was may be used before 18 hr)
And the blood in it was totally clot.
Even I don’t know his/her status (i.e he/she was positive or negative) from HIV
Next day I take 1st dose of pep at 2:00pm (i.e after 26 hr)
So tell me what kind of things should I have to do
HI Yudatadei, please see here for more information about PEP: https://i-base.info/qa/factsheets/pep-faq
I started pep soon after 4 days post exposure is it sure once using correctly will be safe after pep?
Hi Miosi, yes PEP will still be effective. As you started within 72 hours it will still work.
For more information about PEP please see here: https://i-base.info/qa/factsheets/pep-faq
I had unprotected insertive vaginal sex with a woman, who was having a lot of partners and changing them a lot. I have genital herpes, but no flare up was present. Day after, she claimed that she is + and not on treatment. Day after I managed to get on PEP (now 3 days already) on the 66 hour after unprotected sex. Am I too late? What are my chances to get out of this situqtion negative? Is PEP still efficient when taken at this hour? How to ease my anexiety which is almost unbearable as I am unable to work or function normally. Grateful for tour response