I am a gay male with some PREP related questions. For what it's worth I am HSV2 pos.

1) About a week before I started Prep I had a sexual encounter with someone who is on the promiscuous side. I read an article that people who acquire HIV immediately before starting PREP can return false negatives on future tests but didn't say if this would go on forever. Let's say I acquired HIV from that person Will I continue to come back negative until such time as I completely stop PREP? Or would I eventually come back positive on a test without having to stop PREP? The article I read mentioned there might be a delay in coming back positive, but didn't say how long the delay would be.

2) Most of my friends use PREP as an excuse to abandon condoms. Where do you stand on this? Is a person who stops using condom more likely to get HIV even though they are on PREP? I personally haven't stopped using condoms because of my HSV2. But I am curious where you stand on going condom free while on PREP as it relates to HIV. It goes without saying that going condom free increases the likelihood of getting any number of non-HIV STD's.

3). Are there any implications for me as someone with HSV2? I know that unprotected I am more likely to get HIV because of my herpes. Is PREP somehow less effective because of my herpes? Will my partners being on PREP give any protection to them against getting my herpes?

Thanks!

You don't say how long you've now been on PrEP.  Presuming that you had a negative 4th generation (antigen/antibody) HIV test when you started PrEP{ Prep in not fully effective until about 7 days after starting it.  Thus, on fortunately rather rare occasions, persons become infected either just before they start PrEP or soon afterwards. In these situations, if a person does become infected, development of positive tests may be delayed because of the effect of the PrEP medications.  That said. persons who do become infected in this situation do ultimately develop positive tests.  While recommendations vary, in part because circumstances vary, it is advisable to someone in your situation to have a 4th generation test monthly for the first 3 months following initiation of PrEP become reducing the frequency of testing.  Alternatively, if you contact the partner you mention and he has had a negative test since your last encounter and is negative, you can be confident you were not exposed.  With this preliminary response, let me address your specific questions:

1.  As I said above, persons acquiring HIV as they start PrEP do develop positive tests but this process may be delayed.  How long varies.  I would anticipate  that if you had acquired HIV, your 4th generation test would be positive by 3 months.

2.  PrEP taken consistently reduces HIV risk almost completely (>99%) but you are still vulnerable to other STIs.  Condoms reduce this risk greatly.  Routine testing for the most common STIs, gonorrhea and chlamydia at all sites of sexual exposure, as well as syphilis blood tests are recommended, typically about once every 3-6  months depending on the frequency of exposure.  

3.  Your HSV increased your risk for acquisition of HIV if exposed before you started PrEP.  There are no data to suggest than once on PrEP, you are at any higher risk for the rare PrEP failures than anyone else.

I hope that this information is helpful.  If any part of my response is unclear, please use your up to two follow-ups for clarification.  EWH

You asked about my timeline. Mine is a little funky:

On 2/4 I have my first sexual encounter with said guy

On 2/18 I have my second sexual encounter with said guy

On 2/28 I started PREP. I got a negative HIV test result immediately before starting PREP...I think it was just a day or two before my first pill.

-On 3/4 I have my third sexual encounter with said guy.

-On 3/20 I stopped prep because I knew I was going out of town for about a month and wouldn't be having any sexual encounters so thought I might give my kidneys a break.

-On 4/20 I received a negative result on what I am guessing was a 4th generation test.

-On 4/21 I resumed the PREP

So, as you can see, there was a month gap in my PREP. 

But am I reading your answer correctly that if someone were to acquire HIV shortly before starting PREP,  they would most likely show up as positive by the three month mark? And this would be true of someone who, unlike me, had been taking PREP consistently for all three months (with no missed doses)?

Thanks Dr Hook