Spotlight Center on HIV Prevention Today

Zero HIV Infections Seen Through Condomless Sex When HIV-Positive Partner Is on Effective Treatment

March 4, 2014

Zero cases of HIV transmission were observed in mixed-status couples when the HIV-positive partner was on treatment with a viral load below 200, according to a study presented by Alison Rodger, M.D., at CROI 2014 in Boston. However, the result comes with many caveats and does not condone condomless sex, nor does it indicate that transmission is impossible with effective treatment.

The trial, known as the PARTNER study, followed 767 mixed-status couples in 75 sites across 14 European countries. The couples provided informed consent, with the negative partner knowing about the positive partner's status and risk of HIV transmission, as well as being educated about the need for consistent condom use.

To be eligible for follow-up, the couples had to report condomless sex, not using PrEP (pre-exposure prophylaxis) or PEP (post-exposure prophylaxis) and having a viral load below 200 within the last year. Data was collected every six months, in the form of a confidential risk-behavior questionnaire, along with a viral load test for the positive partner and an HIV test for the negative partner. Overall, the participants provided 894 eligible couple-years of follow up (CYFU), with an estimated total number of condomless sex acts at about 44,400.

The study included 445 heterosexual couples and 282 men who have sex with men (MSM) couples. Out of the positive partners, the median age was around 42, with at least 94% reporting treatment adherence over 90% and at least 85% reporting an undetectable viral load.

For the negative partners, the median age was also around 42, with reports of having consistent condomless sex for a median of about 2.5 years. For the men and women in heterosexual couples, diagnosis with a sexually transmitted infection (STI) other than HIV was at 5% and 6%, respectively, while reported condomless sex with partners outside of the relationship was 3% and 4%. However, for the men in MSM couples, STI diagnosis was at 16% and reported condomless sex with other partners was 34%.

Surprisingly, there were zero linked cases of HIV transmission within couples. However, here's where the numbers and statistics get a little tricky. While the estimated rate of HIV transmission within couples (per 100 CYFU) for any type of sex was zero, the confidence interval (CI) was 95% and the upper bound for this interval was 0.4, translating into a 10-year risk of about 4%.

Similarly, while the estimated rate of HIV transmission within couples (per 100 CYFU) for anal sex was zero, the confidence interval (CI) was 95% and the upper bound for this interval was 0.96, translating into a 10-year risk of about 10%.

Furthermore, looking at type of sex reported by the negative partner, all estimated rates of HIV transmission within couples (per 100 CYFU) were zero. However, the upper bounds of these confidence intervals varied:

  • For women, vaginal sex with ejaculation: 1.88.
  • For men, vaginal sex: about 1.32.
  • MSM insertive anal sex: about 1.37.
  • MSM receptive anal sex without ejaculation: about 2.5.
  • MSM receptive anal sex with ejaculation: 4, translating into a 10-year risk of about 32%.

It's also important to note that during the study, HIV transmissions that were not phylogenetically linked to the positive partner did occur through partners outside of the relationship. According to Rodger, the total number of actual transmissions will remain blinded until the end of the study, and further research will be conducted to focus on the risk of transmission specifically among MSM.

As a reminder, the upper limits of risk remain uncertain, particularly over receptive anal sex with ejaculation, so while these results are promising, they require further investigating and do not condone condomless sex.

[Editor's note: To help better understand the statistics: Joel Gallant, M.D., M.P.H., writes in his blog, "While the transmission rate was zero in this study, the presenter made a point of discussing the uncertainty around that number. [Rodger] pointed out that while their best estimate for the transmission rate is zero, they can’t exclude the possibility, with 95% certainty, that the true overall transmission rate was up to 4% over 10 years, and that the true transmission rate for receptive anal sex with ejaculation was up to 10% over 10 years. This is basically a statistical way of saying that you can’t prove a negative. As the study accumulates more couples, the statistical uncertainty will diminish, and if they continue to see no transmissions, they will be able to say with greater certainty that the estimated risk is zero."]

Warren Tong is the research editor for and

Follow Warren on Twitter: @WarrenAtTheBody.

Copyright © 2014 Remedy Health Media, LLC. All rights reserved.

This article was provided by TheBodyPRO. It is a part of the publication The 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014).

Reader Comments:

Comment by: Timmm55 (Palm Springs CA) Wed., Apr. 29, 2015 at 5:16 pm UTC
Also worth noting is that POZ undetectable people are tested every 3-4 months....including other STDs. Most "neg" guys are less frequent.
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Comment by: THULANI MOTAUNG (ITSOSENG NW SOUTH AFRICA) Mon., Sep. 22, 2014 at 12:00 pm UTC
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Comment by: thato (pretoria) Tue., Feb. 24, 2015 at 3:14 am UTC
hi thuli home is also Itsoseng( NW) but currently work and stay in pretoria i was also indenial following the Dissidents group but later i faced reality and decided to live positevly and start treatment, now iam undetectable living happy with my status

Comment by: Tholang J Moleleki (Lesotho) Mon., Mar. 24, 2014 at 7:51 am UTC
i guess this is highly possibly..given the fact that the positive partner is really effective with medication
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Comment by: PK (Surrey BC Canada) Wed., Mar. 19, 2014 at 11:24 am UTC
There is more to worry about these days than HIV. In Vancouver there is an epidemic of syphillis going around. I have a bottom FB who has a GF who had to call me to tell me he was reactive to syphillis. His GF and I both had to get tested and get shots. Good news is neither of us got it but it is a stark reminder of what can happen if you don't test often if you play bare and don't test. Here in Vancouver there is an aggressive move to have people test. We now have a free rapid HIV test with results in 5 minutes and a early HIV test that detects HIV in 2 weeks after being exposed. Moral of the story is, if you play bare get tested often.
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Comment by: PP (Berlin, Germany) Wed., Mar. 26, 2014 at 12:02 am UTC
And in Berlin there is an epidemic of gonorrhea and HPV, people here don't care much about HIV transmission with undetectable VL, but STDs are skyrocketting. Trust me first guy i had unprotected sex in 3 years (anal receptive without ejaculation) and left me with terrific chancre+gonorrhea bonus. It hurts that the guy was still OK with trying a relationship, but kept his disease quiet for weeks until i just couldn't bear anymore the pain and the disgusting discharge and went to the doctor. The antibiotics killed the infection, but nevertheless the ulcer remains and still some discharge... disgusting, never ever receptive anal sex for me again... i may even need surgery next month. I read that even with protection gonorrhea is highly contagious (50-95% transmission risk compared to 1-4% for HIV)

Comment by: Paul (Chicago) Wed., Mar. 19, 2014 at 8:37 am UTC
Since I now test every 4 months There is always the risk of having my viral load increase without my knowledge, I still use condoms.
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Comment by: James (Wv) Fri., Mar. 14, 2014 at 3:36 pm UTC
This confirm my experience with my poz partner. I have been bottom for him bare for eight months no transmission. He has been udvl for twelve years and we have been together the same span. I was comfortable going bare after some research. I think under the right conditions bare is back for committed magnetic couples.
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Comment by: David Kelly (Pahoa HI) Wed., Mar. 12, 2014 at 2:41 pm UTC
My husband and I have been together over 20 years. I am poz he WAS neg.
Thanks to reports like this we decided to play without condoms, since I was and am undetectable. We made this decision after meeting with my Dr. Long story short....we are now BOTH POZ. To everyone and anyone having sex...the only way to stay neg is to bag it and even then that is not always going to protect you! BE SAFE AND USE A CONDOM EVERY TIME !!!!!
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Comment by: Timmm55 (Palm Springs CA) Wed., Apr. 29, 2015 at 5:11 pm UTC
No where does it say you, or your partner, are 100% monogamous.

In the Partners Study the only transmissions occurred from outside the relationship, with the negative partner. It was genetically tested and proven.

The undetectable partner was PROTECTING his partner. He was PREVENTING HIV transmission.

Maybe that gave the negative partner a false sense of security. That security ends when away from his undetectable partner. If you don't know or aren't sure of your partner's status use a condom.
In the HPTB-052 study the only transmissions occurred when the partner wasn't yet fully suppressed. Starting treatment does not equal sustained repressed viral load.
The "confidence" rate includes these 2 sets people. They were a part of the study and must be included.

Although it didn't happen in any of the studies, non-compliance or a drug holiday will certainly make an undetectable person HIGHLY infectious.

In a nut shell, don't blame the meds for your partner becoming POZ. There was a human error involved.

Comment by: James (Munich, DE) Tue., Mar. 11, 2014 at 11:00 pm UTC
I am having receptive anal sex w/ejaculation for awhile and nothing has changed. We both are on meds, undetectable, his CD is 550, mine is 1400.
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Comment by: Peter P (San Diego) Tue., Mar. 11, 2014 at 9:12 pm UTC
Give it a rest.. Condomless sex is happening.. I'm very happy these results are finally documenting what we already knew to be true..
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Comment by: John-Manuel Andriote (Norwich, CT) Tue., Mar. 11, 2014 at 7:59 pm UTC
Unfortunately, one of the most important caveats about data like these for gay/bi men (MSM) is that many (most?) men are versatile where it comes to anal intercourse: tonight's bottom is tomorrow's top. This makes it hard/impossible to isolate precisely which "act" might be "the one" that infects someone.

Other important figures I don't see addressed in other comments:

* 5 -6 % of the hetero couples had other other sexually transmitted infections--compared to 16% of MSM, so these coupled MSM have as much as three times the rate of other STIs besides HIV.

* 3 - 4 % of the hetero couples report condomless sex with other partners than their primary partner, compared to 34 % of the MSM, 10 times the rate of the hetero couples.

* MSM receptive anal intercourse with ejaculation carried a 10-year risk of 32 %.

I'd call those pretty sobering statistics from a gay/bi man's point of view. And as reported, HIV infections did occur from partners outside the relationships but they were not included--and the total number of new HIV infections is blinded until the end of the study.

Important consideration for those jumping for premature joy about condomless anal intercourse for gay/bi men: If we don't know which partner is top and bottom within the relationship, how do we know who is top/bottom outside the relationship? Maybe a top is a bottom outside the relationship--and brings HIV or something else home with him?
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Comment by: Casey Charles (dundee scotland) Tue., Mar. 11, 2014 at 6:33 am UTC
what do you mean by "confidence interval"?
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Comment by: Warren ( Tue., Mar. 11, 2014 at 6:52 pm UTC
the confidence interval is just a statistical way of describing estimates. because even though the actual study found zero transmissions, there can still be a margin for error. therefore, they estimate, with 95% certainty, that the risk can be as low as zero or as high as 4%.

i've added a note at the end of the article to better understand this.

Comment by: michael (los angles) Tue., Mar. 11, 2014 at 5:35 am UTC
this study is important because it can become another stepping stone into tearing down the wall of stigma.....maybe if people knew that once the virus is controlled, safer precautions such as condoms will make it almost impossible to contract the virus....then maybe people will not look upon positive people as zombies that are too dirty to touch.
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Comment by: Peter P (San Diego) Tue., Mar. 11, 2014 at 9:15 pm UTC
Don't hold your breath..,
Comment by: Blaine B (LA) Tue., Mar. 25, 2014 at 1:18 am UTC
We're talking about an STD that is in many populations both common and manageable. Still, the stigma persists. It's naive to pretend that self preservation has anything to do with what we're witnessing.

Comment by: John Rodriquez Corpus (Fort Worth, Texas) Fri., Mar. 7, 2014 at 3:58 pm UTC
As for going condomless remember there are still other STI, Sexually Transmitted Infections to avoid.
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Comment by: Mark S. King (Washington, DC) Thu., Mar. 6, 2014 at 6:42 pm UTC
Does anyone "condone" condomless sex? The actuaries mentioned in this article don't present a particularly big "but" to me. It appears that study participants were at less risk than the general population, and less than oral sex with a stranger, for instance, and we know how common condom usage is for that.

I appreciate the qualifiers, but they seem overly careful in light of the number of infections that occurred among couples in this study: ZERO.
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Comment by: Sean (Brooklyn NY) Thu., Mar. 6, 2014 at 5:50 pm UTC
Could you please explain the terms "confidence interval" and "upper bound?" It is confusing that a risk factor was extrapolated from zero transmissions. Thanks!
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