I started Prep for four days and I had unprotected sex with a random military person I don't know, and I ejaculated in him. He told me he was negative and asked me repeatedly if I was negative and I told him I was on Prep. He reassured me he was negative because he is in the medical field and if you are HIV+ you have to be cross trained out of your job. Anyways, I took the pill on the forth day (the day we had unprotected sex) and I have taken it ever since and this is my 14th day on the medication. Do I need to be seen or tested in the 90 day period or will the medication be okay to continue to use? Am I at low risk? What are the chances the medication does not provide the protection within that 4 day window? What is the actual timeline for the medication to work? I read online that the receptive parter that uses Truvada has maximum protection after 7 days and insertive parters are 20 days? Others say 4 days is enough time if you continue to use it. Please advise. Thank you.
I understand that the information out there is very confusing. Does PrEP protect tops, and if so, how long does it take? In order to answer that we're going to have to be somewhat tolerant of some scientifically ambivalent responses and some "probably's."
But let's start with what we do know. Your risk of acquiring HIV in the scenario you describe is extreme unlikely. Let's say that you weren't on PrEP, and he had detectable levels of HIV in his ass. Even then, your risk of acquiring HIV under those circumstances are exceeding low, less than 1% (https://www.poz.com/article/HIV-risk-25382-5829). When you add in the fact that he is in the military and being screened every 3 months, you reduce that less-than-1% scenario even more.
Now - the million dollar question: Does PrEP protect you as a top after 4 doses? And the answer is: Probably and maybe.
Truth time: Researchers don't know exactly how PrEP works. But they have done samples on rectal tissues and vaginal tissues to measure how Truvada builds up in those areas, and how they are protected after being topped. No similar study has been done for insertive partners (tops). That would involve regular swabbing of the inside of the urethra at the head of the penis. It would be very difficult, and possibly unethical, to find a person who would be so willing to endure the pain and discomfort of having the inside of the head of their penis swabbed regularly.
So what do we know about PrEP for tops? We know that no one in any efficacy trial acquired HIV when they took PrEP four or more time a week, whether or not they were top or bottom or vers (https://www.robertmgrant.org/project/has-prep-ever-failed/). And we know that no one in 32 worldwide demonstration projects, which included heterosexual men, and gay/bisexual men, ever became HIV+ when they took PrEP as directed (http://www.natap.org/2016/ICAAC/ICAAC_02.htm). Statistically we know SOME of those guys were tops only.
Based on this evidence, I think it's fair to say that it is highly likey that PrEP protects tops effectively in a way that is similar, if not equal to, how it protects bottoms. Unfortunately we just don't have a study that ONLY looked at topping. And again, I sure wouldn't want to sign up for those urethral swabs.
So for you: Based on the fact that you had 4 doses of PrEP in your system at the time, had condomless intimacy with someone who is tested regularly, AND the risk to tops is so much significantly lower than bottoms, it seems to me you are at near zero risk of having acquired HIV from this encounter.
The CDC protocol recommends that those of us on PrEP get tested every 90 days for HIV. You can always request a test sooner than that if it will help you with your peace of mind.
For more information about PrEP, topping, research, and the knowns and unknowns, please consider joining my Facebook "PrEP Facts" group page at https://www.facebook.com/groups/PrEPFacts/.
Thank you for a great question, and I do you with you health and pleasure in the future.