Un-detectable Un-transmissible Un-ambiguously…

For many years it’s been know that effective HIV treatment reduces or lowers the risk of sexual transmission of HIV. By how much, is now more certain, poignantly in the absence of condom use.

Previous landmark studies (namely HPTN052) measured the protective benefits of HIV treatment PLUS condom use combined, proving 96% reduction in HIV transmission risk predominantly among heterosexual sero-different couples.

Following in its footsteps somewhat, the PARTNER study has now directly measured HIV treatment prevention benefits in absence of condom use. More-over, it has now measured this in gay men in sero-different relationships with the HIV positive partner on treatment, virus undetectable and not using condoms for anal sex…for which until now there has been no direct evidence at all.

The PARTNER study 2 year results presented at the CROI conference (Boston) this year (CROI webcasts) offer impressive quantifiable, unambiguous, new landmark findings that clearly demonstrate the potent effect of using HIV treatment as prevention (TasP). A short summary of study characteristics, results, and implications follows:

  • 767 sero-different couples (40% gay men/MSM), not using condoms, not using PEP, not using PrEP.
  • HIV-positive partners on antiretroviral treatment 5 years (gay men, 97% undetectable viral load) and 7-10 years (heterosexuals, 94% undetectable viral load). The cut-off point was 200 copies/ml plasma (blood) viral load.
  • Not using condoms for [median] 1.5 years (gay men) and 2.5 years (heterosexuals) – amounting to 16,400 condom-less sex acts (gay men) and 28,000 (heterosexual HIV-negative males and females combined).
  • No (Zero) HIV transmissions occurred between partners in the study with undetectable viral load. Transmissions occurred outside the study couples, due to sex outside the study relationship, but none (zero) were linked to the HIV-positive partner in the study.

Whilst the study observed the risk of someone transmitting HIV with an undetectable viral load is zero, upon stricter analysis with a 95% confidence level, there remains uncertainty about the upper limit of risk especially for receptive anal sex with ejaculation – estimated to be at most a 4% risk (2% for vaginal sex with ejaculation).  However,  the researchers suggest the true likelihood is closer to zero = extremely low risk in the presence of undetectable viral load. The lowest risk is for vaginal sex estimated at 1% risk of transmission to the insertive male. At worst, we can say this evidence shows that if your viral load is in the range below < 200 to undetectable, the risk of transmission of HIV without condoms is somewhere between 1% and 4% (depending on sex act). At best, we can say the observed probability, so far, is zero (contingent upon sex act).

The Swiss Statement, issued in 2008, claimed that on treatment with fully suppressed viral load for at least 6 months the risk of HIV transmission was zero (“un-infectious”), so long as there were no STIs present; but the PARTNER study hasn’t found that signal so far. Non-condom use opens up the risk of getting STIs– but perhaps this a moot point in this otherwise exciting context, nonetheless a relative one.

The study is continuing until 2017 – PARTNER 2 – whereby we need to wait out for the final results to garner more precise absolute and relative risk estimates (particularly among gay men and anal sex), as things could change over time by longer observation period.

Importantly, this study demographic to-date estimates a 3.9% risk of HIV transmission over 10 years for any sex, and a 9.2% risk over 10 years for anal sex. There still seems to be residual risk of transmission in absence of condoms, albeit very low and unlikely.

Despite these monumental and encouraging new findings, the principle investigator of this study – Jens Lundgren – suggests it may never be possible to show with certainty that the risk of HIV transmission on effective HIV treatment with well supressed viral load is absolutely zero.  However, we at QPP think that the PARTNER study goes a long way in refining and defining the debate around treatment as prevention!

Is it safe to stop using condoms if I have undetectable viral load? Investigators of the PARTNER study recommend continued use of condoms until the follow-up study results are available to confirm the current interim findings.

In that context, currently we cannot say that that risk of not using condoms is absolutely zero infection risk. New light on old conventions is challenging for us all. We must each consider our own personal risks – to ourselves and others. All this study can presently provide is information about the risk of HIV transmission when not using a condom.  It is also relevant information for HIV-negative individuals in sero-different relationships. Within causal sex settings there are likely to be additional risks and confounders, as this study also indicates.

What if I am not on HIV treatment, should I be? Not necessarily, although you can start HIV when you want and early treatment reduces the damage HIV does to your body. Discuss the best time for you to start HIV treatment with your doctor. Taking treatment for prevention benefits  may be an additional consideration in starting treatment, but condoms are still recommended for HIV prevention – as this study shows the risk of not using condoms in the presence of undetectable viral load is not fully quantified.

Importantly, whilst this research is indeed convincing scientific research, it is NOT law, and neither has it been used and tested in a legal case in accordance with the law. Under the Queensland Public Health Act you must disclose your HIV to any sex partner (regardless of viral load) if condoms are not used.

Want More Information?  Of course you can always discuss this with staff at QPP, and we encourage you to also talk with your clinic about the implications and your personal situations and circumstances.

Further Reading:

Study Reference:

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