Welcome to the forum. Thanks for your question.
Congratulations for a responsible approach to sex with other men. You're doing everything right -- not only condom use for anal sex, but equally important, doing your best to determine your partners' HIV status and avoiding sex (I assume) with those who are infected (and not on treatment) or who don't know or are evasive about it. Keep up these habits, and you can expect to never catch HIV -- and it is very unlikely you caught it this time.
OK, now to your specific questions. Obviously, the precautions you took are not perfect. Condoms do fail, as happened this time; and the occaional apparently negative partner may in fact have an as yet undiagnosed HIV infection. But even though receptive anal sex with an infected partner is the highest risk sexual practice there is, on average only about 1 in 200 such exposures results in HIV infection. And it remains highly probable your partner doesn't have HIV. If we assume a 1% chance your partner had HIV despite his belief he does not, then the calculated odds you would catch HIV come to 1 in 20,000 (0.05 x 0.01 = 0.0005). That's equivalent to haveing a similar exposure once daily for 55 years before transmission might be expected.
That's not to say PEP wasn't warranted. It's a judgment call, and your desire to be maximally safe was properly taken into account (once you helped educate the doctor you saw!). But I wanted to make the point that the odds were very strongly in your favor even without PEP.
How well does PEP work? It really isn't known very well. It's believed to be highly effective from studies in animals, and by analysis of health care providers exposed by contaminated sharp instruments. But it's pretty much guesswork for sexual exposures. My guess is that it's at least 90% effective. If so, that drops the odds you will develop HIV from 1 in 20,000 to 1 in 200,000.
My final advice is that you speak with your partner, whom you presumably should be able to contact. Ask him to be re-tested for HIV. If a new blood test is negative, you could safely stop PEP and cease all worry.
Your comment below implies that your own doctor is on top of things. Follow his advice about follow-up testing. But in the meantime, stay mellow. Almost certainly all will be well.
Best wishes-- HHH, MD
By the way, I only went to an urgent care clinic because my doctor could not see me right away. He will be monitoring me for the next four weeks.
Thanks for your detailed response, doctor. I appreciate it.
As you advise above, I tried to contact my partner to request that he be tested for HIV. Unfortunately, he seems disinclined to respond to me. This evasive behavior weakens my faith in his veracity about his HIV status.
The probabilities you provided above were very helpful. Thank you. Even if I adjusted for significantly higher numbers, the odds seem to stay in my favor:
20% chance he was infected, 20% chance of transmission, 20% chance of PEP failure = 0.8% chance of infection.
I picked huge numbers to make a point; I understand that the first two numbers are too high to match reality. Is my math correct?
As an aside, the PEP side effects kicked in today. Let me just say that I have nothing but admiration for HIV positive patients who religiously adhere to their regimens.
I agree with your calculation, and you make the point well. Even in a worst case scenario, the odds are strongly in your favor.
Most side effects with the common HIV drugs (Atripla, Truvada, etc) don't continue; my guess is you'll end up tolerating the PEP quite well over the time you are taking the treatment.
Just an update to say thanks for your help, doctor. The fifth of July was a scary day for me, and you helped me keep a cool head.
Thanks for the thanks. I'm glad to have helped.
Sorry to revive this thread, but my doctor and I have a question that you can probably answer. We're following the standard recommendations for HIV testing with PEP (baseline, six weeks, three months, six months). What we'd like to know is how much faith we can assign to the results of the six week test, since PEP is one of the only things that can actually delay seroconversion.
There are no solid data on which to base a recommendation on time to testing after PEP. Most experts follow the schedule outlined by your doctor. My guess is that negative results are quite reliable by 6 weeks and certainly by 3 months, but that's all it is -- an educated guess.
That's kinda what I figured. Thanks again.