Q and A

Question

Is PEP effective if taken 48 hours after exposure?

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.

822 comments

  1. John

    Hei,

    A month ago I had Anal sex with someone ( I was the active one) and the condom broke. Because I didn’t know their HIV status at the time I began taking PEP 15h -after exposure. In the beginning I had side effects such as mild nausea, diarrhea and big apetite)
    3weeks after the start I got mild rash on chest, back, neck/beard area ( the doctor wouldn’t even call it a rash because it was just a few red spots ) and redness around the nose.

    QUESTION
    It is 2 days after I Finished the PEP and I still have some of the symptoms ( the rash (itchy one), and the tightness in the throat , sometimes nausea , the sleeping discomfort and the dry lips).

    Is it possible that this is allergy to the PeP pills (Emtricitabine/tenofovir ’blue’ and Raltegravir (Isentress®) ‘yellow’) I took and how long after pep they will be there ? ( also I still have the big apetite)

  2. Roy Trevelion

    Hi Robs,

    It’s not easy to answer your question. Unfortunately, there is no data showing a difference between 21 and 28 days of PEP. Please see this Q&A.

    However, as Angeina says above, the earlier PEP is started, the more likely it could work. Ideally, this should be within a couple of hours. If this is not possible, then still the earlier the better.

  3. Robs

    Hi
    My partner and I were taking PEP for the last month he finished a week earlier than me. We had unprotected sex together and I’m now a bit worried about the outcome though we both tested hiv negative before starting PEP. Does this recent exposure increase the chances of getting HIV after 4days of completing PEP?

  4. Lisa Thorley

    Hi Julia,

    If there are trust issues, the easiest thing is to use PEP and then get tested.

  5. Julia

    Hy i sleep with someone i don’t know his status we use protection but the condom broke i don’t trust him so should i get infected

  6. Roy Trevelion

    Hi Skakes,

    Please see the reply below to your first comment.

    Here’s the guide to PEP

  7. Skakes

    i slept with an hiv position pregnant woman who is on treatment and the pregnancy is not mine…i started taking pep after 40 hours and now im having fever and night sweat please help

  8. Roy Trevelion

    Hi Skakes,

    It’s good that your partner is on HIV medication. That’s because it’s the best way to look after her health, and her baby’s health too.

    If she has been on treatment and now has an undetectable viral load, then the risk of HIV transmission is zero.

    Please see Undetectable = Untransmittable (U=U) here.

  9. Skakes

    i slept with an HIV positive pregnant woman who is on medication and the condom broke

  10. Roy Trevelion

    Hi Mr. Worry,

    Was the combo test you had 95 days after finishing PEP a 4th generation test?

    The window period for a 4th generation antigen/antibody test is about four weeks. By this time 95% of infections will be detected. There is a three month window period after exposure, for the confirmatory result to detect more than 99.9% of infections. Please see this link to window periods.

    So it looks like this result is more than 99.9% accurate.

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