PrEP and multiple loads?


Hello Damon,

I am a big fan of what PrEP has done already and what it can do for the future. I'm also aware that it is a medicine and nothing is guaranteed 100 percent. I have a question which I was unsure about. If you were on PrEP and you took multiple loads, could you be at a higher risk of a HIV infection? If some of those loads were detectable, do they accumulate to become a greater risk than say one load?

Also, if I was on PrEP, and I have an STI, and took multiple loads, does this increase the risk of transmission?

I have been HIV positive for 11 years and currently present talks on living with HIV. This question is one that has come up recently of which I've not been able to find the answer to. I would appreciate an expert's opinion to shed some light on this area.


Thank you so much for the work you are doing to help people learn pleasurable ways to prevent HIV. I also do a lot of speaking about PrEP, and this question comes up for me from time to time as well.

The short answer is that there is no definitive conclusive evidence on this matter. There is some compelling evidence to point toward the answer being "no", that taking multiple detectable loads of HIV does not compromise PrEP's efficacy. But some new data suggests that may not be completely certain.

So let's start with what we do know. There have been more than 11,901 individuals who have participated in safety and efficacy trials for PrEP ( In order to participate in one of the trials, you had to be considered at relatively "high risk" of contracting HIV. Many participants were gay and bisexual men who were having condomless receptive anal sex with partners of detectable and unknown HIV statuses.

Although the researchers did not specify, we are well aware that in a population sample this large it is almost guaranteed that some were having receptive sex in group situations where multiple loads were received. Yet within this sample there was not one single HIV acquisition among participants who took the drug as prescribed. To compare and contrast, there were significant HIV acquisitions in participants that were given a placebo, and/or did not take the drug as prescribed.

Now put that together and it adds up: Receptive anal sex encounters, even with detectable HIV+ partners, are protected by PrEP when used as directed. So far, so good.

However, a new case published in February 2017 appears to challenge this idea. It was reported that a 50-year-old cisgender gay man became HIV positive eight months after starting PrEP. He was in a research trial in Amsterdam, and therefore there was excellent documentation of his consistent adherence to PrEP. The patient tested negative for HIV at the start of PrEP, and again at one month, three months and six months before he tested positive.

The patient reported an average of about 50 anal sex partners per month before diagnosis. He also reported having condomless anal sex on about 50% of the days before diagnosis. The median number of sex partners per day with condomless anal sex ranged between two to five each month. Additionally, the patient experienced two instances of rectal gonorrhea and one instance of rectal Chlamydia. He also reported using drugs during sex, including amphetamine, cocaine, mephedrone and ketamine. (

So what does this mean, and what does this explain? Unfortunately, not a whole heck of a lot. Although the quantity of sexual partners, multiple loads, drug use, and concurrent instances of having STIs may have contributed to PrEP's failure here, the researchers can not be certain of that.

Dr. Elske Hoornenborg, an infectious disease specialist at Public Health Service Amsterdam who supervised this case, offered her own perspective on some of these mysteries and hypotheses brought up by this case: But given this was an isolated case that hasn't been similarly reported or documented anywhere else, for now we just have to say it was an anomaly and hope that in the future we will understand more.

So when people ask you this question, I would simply say, "PrEP appears to offer significant protection 99% of the time regardless of multiple loads and detectable HIV statuses. However, we have one instance where it may not have protected sufficiently under these conditions. As far as we know that is still 99%."

For more information and discussion, please visit the international Facebook "PrEP Facts" page at