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 Mpumi, please follow this link for more information: https://i-base.info/qa/factsheets/hiv-transmission-and-testing
I had sex with my new boyfriend so he removed de condom during intimacy I noticed before we finished nd I dnt knw his status so should I be worried
Hi Tony, PEP can still be effective – using PEP within 72 hours is recommended by guidelines to still be effective in this time frame.
If you used a condom there is no risk of transmission – though if you do not remember this cannot be certain. Transmission to your wife is extremely low risk but while you are unsure of your status, continuing to have sex without a condom is not recommended – or other protection e.g., your wife on PrEP.
Hi. I started on PEP 55 hours after possible exposure. Can it still be effective? Had sex with sex worker and really worried I started too late. I went out drinking and remember I had a condom but don’t remember the rest. I have lost my apetite. Also I will need to let my wife know as I don’t want to risk anything. 12 years down the drain. :(
Hi Trevour, after 72 hours how well PEP works is reduced, if at all. It might have some effect but starting this late after exposure, it is unlikely to be effective.
having pep in period of 93 hours can it still work
Hi Johannes, while you are on PEP you cannot be sure of your status. However, PEP would be suppressing any HIV in your body. This means your parter will not need to have their own course of PEP – though it would be recommended to test when they can.
After 25 days it is more than likely that PEP will have worked.
I also have a question, I have taken PEP for now 25 days. I had unsafe sex with my partner who is negative on day 25 of taking PEP.
Can I transmit HIV to her while on PEP treatment? Or is it safe? Am worried
Hi Tim, I understand why you may be feeling anxious however there are a number of factors on this occasion that will significantly reduce your risk.
This escort that you slept with did state that they are on PrEP. Often sex works are most aware of their own sexual health – more so than the general population. Stating that she is on PrEP would suggest she is being conscious about her own status. Being on PrEP would suggest that if she was positive, she would be compliant with ART.
More so is that you were the insertive partner. In this case your risk of transmission is half that of being the receptive partner.
Your adherence being diligent is very encouraging. This is what most commonly causes PEP to be effective or not. PEP is difficult to apply to humans as it is not ethical to purposefully transmit HIV to determine how effective PEP is. Animal studies while useful, cannot be completely applied to humans – there are too many differences to make animal models exact.
There are differences between countries for time effectiveness of PEP. This is based on said animal studies. However before 72 hours there is still ~80% effectiveness. It is also important to note that you started PEP much closer to 48 than 72 hours.
In the UK this would be considered very low risk and it is very likely you would not be considered suitable for PEP. This is because the course of PEP would cause more negative side effects than the very small risk of transmission. It would be very unlikely that you will test positive after this.
Please follow this link for information about anxiety and fear around testing: https://i-base.info/guides/testing/hiv-testing-feelings-of-fear-anxiety-and-guilt
Hi, I have a question in the same vein of this thread, about PEP. I live in NYC, and after a night of heavy drinking I engaged in unprotected anal intercourse with a MTF trans escort whose HIV status was unknown (although she did tell me prior that she is on PrEP). I was the insertive partner. We had sex two different times over the course of about 90 minutes. Both times ended with me ejaculating inside of her anus. I was prescribed Truvada and Isentress and took my first does of both 53 hours after the sex.
In my research since the incident, it looks like that might have been a bit too late – despite the guidelines stating it is effective in helping to reduce the likelihood of transmission if started within 72 hours. This particular article discusses the lessened efficacy after 48 hours in animal studies:
https://www.aidsmap.com/news/mar-2020/new-pep-studies-revive-interest-post-exposure-prevention
I am a week into the PEP course and have been very diligent about taking my medication at the exact time everyday (morning and night) and will continue to do so for the remainder of the 28 days. I have been racked with anxiety since this happened a little over a week ago. Can someone please comment on how likely I am to go on to test positive after this?