45 loads in 7 days - is PrEP even a factor?

[Pighole88]

I've been on PrEP for about 8 months now, and have taken it diligently every day. I would occasionally bareback, usually with friends, and any poz tops were always undetectable (so they said).

That said, in the last week I took 45 anonymous loads - a decision I'm not regretting because it's something I've always wanted to do. However, other risks aside (HSV, Hep C, Syph), What are your opinions on how much I can rely on PrEP at this point?

I was told that it was up to 98% effective in preventing transmission of HIV. UP TO 98%, which means there's a chance that it could be lower.

Has anyone else been on PrEP and still converted?

[Guest JizzDumpWI]

If your ID doc is anything like mine he/she will want you to take a full STI panel every three months. When was your last full STI test? If you are just a month out, test just a little earlier. If you tested a month ago, wait two weeks and test again...

[pigpozdad]

Have you continued taking loads, to break the 45 barrier??

[Guest JizzDumpWI]

45 in seven days is a "barrier"?

[pigpozdad]

did he go past the 45 load goal

[wood]

Well obviously even with PrEP, you have an increased risk, but yeah the advantage of PrEP is that you still get a significant amount of protection from it even with exposure. Now obviously that is a lot of potential exposure, but if some of the guys were already on medication, that further lowers your risk. I doubt many were neg, but obviously there is no risk from them.

Lets look at it this way, your risk of contracting HIV from an infected source during receptive anal sex is .03-3% chance. Considering some were neg, some were undetectable, and you were on PrEP which significantly reduces your risk, Id venture that during your entire week long session you have about a 1-2% chance of converting, although I would more than likely bet you have some other STD now. That being said if you want to stay neg make sure you keep taking your meds at exactly the same time daily.

[PhoenixGeoff]

OK, lets talk math here and clear up the discussion. We're talking about a branch of mathematics called probability.

I'm going to assume some numbers. First, that your odds of infection without PrEP are about 3%, if you allow a guy with HIV to fuck you and come in your ass. (I'm assuming for the same of simplicity that he's not on meds, you know he has HIV, etc.) Next, we'll assume that PrEP cuts your risk in half to 1.5% (this is a little overoptimistic for PrEP, but not much). What are the chances if you take 45 loads that you'll contract HIV?

As it turns out, it's:

1 - (97⁴⁵/100⁴⁵) without PrEP (or about 75%)

1 - (98.5⁴⁵/100⁴⁵) without PrEP (or about 50%)

Remember: this assumes that all of the guys who fucked you had HIV, all of them came in your ass, none of them were on meds and no-one had extraneous conditions (other STDs, drug use, etc.), including you.

Now, have you significantly tilted the odds in your favor by using PrEP? You bet. Would you still have a pretty big chance of contracting HIV? You bet.

Now, with more information (prevalence of HIV among men who bareback in your community, prevalence of untreated HIV vs. treated, etc., etc.) we could refine those numbers a bit.

But the reality is that if you are going to be sexually promiscuous and bareback routinely, then HIV has a good chance of eventually catching up with you, PrEP or no PrEP.

Long story short, it's not a license to be a pig without consequences.

[PhoenixGeoff]

I'm kind of curious so I found some of the data I suggested. I'll crunch through the numbers again to give you a better idea of your odds. Information on prevalence of HIV among men who have sex with men in San Francisco (where I see you live) is from the CDC. They report that, among all MSM in SF, 23% are HIV positive. Of those men who are HIV+, 19% are unaware of it.

Assumptions: tops and bottoms have the same prevalence of HIV, everyone who is HIV+ and knows it is undetectable, no extraneous conditions (other STDs, drug use, etc.), everyone came in your ass.

There are three scenarios:

1) The top is HIV-, in which case your chance of infection is 0 % (77% of cases)

2) The top is HIV+ and knows it and is therefore on treatment and undetectable, in which case we'll drop the odds of infection by an order of magnitude to 0.3% (18.17% of cases)

3) The top is HIV+ and unaware of it and not on any treatment (including PrEP), in which case we'll leave the odds as originally stated as they are at 3% (4.83% of cases)

Now, say you get fucked and bred once by one random man, the odds of whose status is as listed above. What is the chance that you'll get HIV from that load? The overall odds are 0.19941%, with the bulk of the risk coming from the about 5% of the guys out there who are untreated.

Now, putting that into our calculation above, we find that after taking 45 loads, you'd have a 8.59% chance of coming down with HIV without PrEP and a 4.39% chance of coming down with HIV with PrEP.

Those odds are a lot better than 75% and 50% respectively. But even with PrEP, there's still about a 1 in 20 chance that you just got HIV from your weeklong spree.

Those are significant odds. And the more you get bred, the more those odds increase. Note that the difference between a guy who's not on PrEP who slips up once and you (on PrEP) is a more than 20 times the risk.

Bottom Line: The more promiscuous you are, the more likely you are to get HIV. No other factor (top vs. bottom, condom vs. bareback, PrEP vs. no PrEP, etc.) is anywhere near as significant.

[PhoenixGeoff]

Incidentally, one other thing I found from crunching my numbers is how ineffective serosorting is. As I mentioned above, the bulk of the risk the OP experienced came from men who didn't know they had HIV, even though there were far fewer of them.

I'd also point out that that breakdown covers all men who have sex with men, whether they are monogamous and in a relationship, or total cum whores. But I'd guess that far more of the men who'd turn up to gang fuck an anonymous bottom than 23% would be poz, simply because they themselves are more likely to be promiscuous.

Edited August 21, 2013 by MascMountainMan

[Guest GoodExercise]

PrEP will work right up until it doesn't. With your appetite and love of cum dripping out of your well-used ass, the odds are against PrEP. Then there are adherence issues, etc.

[Pighole88]

Wow, I'm very impressed by your ability to deduce that, MascMountainMan. Thanks for that.

I definitely understand that PrEP is not a get-out-of-jail-free card - and it was only a small factor in my decision to go on a loadspree. I also don't regret anything - it was a matter of living without fulfilling a dream, or living the dream and dealing with the consequences. I chose the latter.

And yes, Hollywoodslut, I'm definitely going to get everything else checked this week. Between bathhouse, gloryhole and cumunion loads, I'm certain I'm not as clean as a whistle right now.

[PhoenixGeoff]

Wow, I'm very impressed by your ability to deduce that, MascMountainMan. Thanks for that.

Thanks man. Actually it turned out to be one of those things that sparked my curiosity a bit and I couldn't stop worrying at it til I figured I'd run through pretty much all the data I had at my disposal. Maybe I'd have enjoyed word problems in school more if they were more along the lines of "If half the football team fucks MascMountainMan in the shower after the game, and half the rest cum in his mouth, then how many loads did he take?"

Just goes to show that we don't get into risky sex cuz we're dumb....

[Blueyedsoul]

Hey guys, great thread. I've enjoyed it especially since I have been pondering to PrEP or not.

[rawTOP]

OK, lets talk math here and clear up the discussion. We're talking about a branch of mathematics called probability…

I don't think you can really do this type of analysis. The most recent data on per-incident risk is from before ARVs came out, and no one really knows how effective PrEP is. As they say "garbage in, garbage out".

[PhoenixGeoff]

I don't think you can really do this type of analysis. The most recent data on per-incident risk is from before ARVs came out, and no one really knows how effective PrEP is. As they say "garbage in, garbage out".

That's true, but I've tried to use conservative numbers. For instance, I think it's unlikely that the risk reduction from a partner with undetectable viral load is more than a tenfold decrease.

The really big variable here is how susceptible your body is to infection. But it seems reasonable to me that whether you happen to be really good at fighting off HIV or drew the short end of the stick in that department genetically, the rate of risk reduction would be more-or-less the same across the board.

If you want to get technical, you can look in these studies for 95% confidence intervals to get some sense of how reliable the numbers probably are.

There is one thing I'd caution here, and that is the power of wishful thinking. If we want something to be true, we tend to discount evidence to the contrary and play up evidence that supports our position. As this is a barebacking site, I'd suggest that our own bias would be towards downplaying the risks that go along with that.

If you are serious about wanting to avoid HIV, for instance, then it makes sense to choose a number towards the top end of the range of estimated risks, as I have here. That gives you a good idea of an upper bound to the risk that you are engaging in. If it turns out to be lower, then great! But it's not wise to assume it's going to be lower. That represents wishful thinking.