Swiss statement that ‘undetectable equals uninfectious’ creates more controversy in Mexico City

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Science took a back seat to politics during one of the most controversial sessions of the XVII International AIDS Conference in Mexico City – one that took place hours before the conference had officially opened. At a specially convened satellite event, seven influential panellists discussed the implications of the Swiss Federal AIDS Commission’s controversial January statement – that an undetectable viral load in the blood renders an individual uninfectious, under optimal conditions.

It became clear during the two-hour meeting that although many on the panel and in the audience argued that there should be honest and effective communication of the facts, ‘facts’ and strongly-held beliefs were often conflated, resulting in even more confusion.

Part of the problem, explained Professor Pietro Vernazza, Head of Infectious Diseases at Cantonal Hospital, St. Gallen, Switzerland and President of the Swiss Federal AIDS Commission, was that the Swiss consensus statement on the effect of treatment on transmission was misinterpreted by some to mean that treatment should replace condoms as a prevention strategy. Others believe that the statement vindicates the practice of condomless sex between non-monogamous partners of different or unknown status practised by small numbers of highly informed HIV-positive gay men with undetectable viral load in some developed countries.


Swiss statement

A 2008 article by a group of Swiss doctors which asserted that people living with HIV who are taking antiretroviral therapy and have an undetectable viral load, with no sexually transmitted infections, do not pass on HIV to their sex partners. Since then, major scientific studies have proven that the statement was correct.

treatment as prevention (TasP)

A public health strategy involving the prompt provision of antiretroviral treatment in people with HIV in order to reduce their risk of transmitting the virus to others through sex.


The Joint United Nations Programme on HIV/AIDS (UNAIDS) brings together the resources of ten United Nations organisations in response to HIV and AIDS.


Having sex without condoms, which used to be called ‘unprotected’ or ‘unsafe’ sex. However, it is now recognised that PrEP and U=U are effective HIV prevention tools, without condoms being required. Nonethless, PrEP and U=U do not protect against other STIs. 

middle income countries

The World Bank classifies countries according to their income: low, lower-middle, upper-middle and high. There are around 50 lower-middle income countries (mostly in Africa and Asia) and around 60 upper-middle income countries (in Africa, Eastern Europe, Asia, Latin America and the Caribbean).

“We never thought of it as a statement that was to be delivered worldwide,” Professor Vernazza told the meeting, but rather “it was meant only to be delivered to Swiss physicians to help them discuss sexual risk-taking with their patients and their steady partners.”

Another problem, noted Professor Vernazza, was that the title of the statement – Les personnes séropositives ne souffrant d’aucune autre MST et suivant un traitment antirétroviral efficace ne transmettent pas le VIH par voie sexuelle (HIV-positive people with no other STIs and on effective antiretroviral therapy do not transmit HIV sexually) – “was misleading and I apologise for that. We wouldn’t do that again.”

He added, however that the statement had noted that even condom use was not 100% ‘safe’, but that the risk was “in a comfortable range that people can live a normal life. We would place sex under antiretroviral therapy in a similarly safe range, but we only consider this ‘safe’ under special conditions,” he said. The conditions include fully suppressive treatment for at least six months, with excellent adherence, regular viral load monitoring, and the certainty that the HIV-positive person and their regular HIV-negative partner have no other sexually transmitted infections (STIs).

“We also made it clear that the only person who can assess perfect adherence and regular check-ups would be a steady partner, and that it should only be the informed [HIV-negative] partner who could assess the risks for themselves.”

The statement, he said, was “good news for a small number of people, but [for everyone else] prevention messages remain unchanged.”

Nevertheless, he conceded that although it was based on an expert assessment of current biological, epidemiological and ecological evidence, the motivation for the statement was primarily political. He said that since it was possible for the Swiss state to prosecute HIV-positive people who had unprotected sex with consenting, fully informed HIV-negative partners under HIV exposure laws, this statement could be used in court to show that if an individual was on successful treatment they could not possibly expose – or transmit – HIV.

He added that the statement was also made to help serodiscordant couples who were unwilling – or unable – to access sperm-washing or other assisted reproduction techniques in order to conceive safely.

Finally, and most importantly, he said, the statement was made because there was a discrepancy between what some doctors told their patients in private and what they were prepared to say in public, and, consequently, to ward off the “risk of uncontrolled diffusion” of information.

Concerns need to be played out

Professor Myron Cohen of the University of North Carolina at Chapel Hill took a more balanced view. Although he said that there was a “very strong biological plausibility” for the scientific conclusions of the Swiss statement, he was unable to agree with the Swiss assessment that the risk of transmission on successful treatment with no other STIs was 1 in 100,000. “I don’t know the actual degree of [treatment’s] benefit or [its] durability,” he said.

He also noted that the Swiss assumption that transmission was not possible below a certain viral load threshold was more of a belief than a fact (and one that was recently rejected by Australasian experts).

However, he did point out that since high concentrations of NRTIs were reached in semen and vaginal fluids, it may have the effect of “bathing whatever virus is present with a [de facto] microbicide.”

Although “there is every reason to think that treatment acts as prevention,” he said, Professor Cohen also had concerns over breakthrough viral blips; breakthrough genital shedding; intermittent STIs, including unrecognised STIs; the gap between increased viral load following treatment failure due to resistance and the next clinical visit; and even drug-resistant superinfection.

“All of these concerns need to be played out,’ he said.

Treatment as prevention

Although Professor Vernazza and his colleagues did not advocate that treatment should be used as a public health prevention tool, it is, argued several speakers, the logical conclusion of the Swiss statement.

IAS President-Elect, Professor Julio Montaner, Clinical Director of the British Columbia Centre for Excellence in HIV/AIDS – who is a vocal proponent of such a public health policy – noted that providing treatment to everyone who requires it for their own health achieves the “double goal of reducing morbidity and mortality and assisting prevention efforts.”

Nancy Padian, Executive Director of Women's Global Health Imperative at the University of California San Francisco expanded on the broader concept of treatment as prevention. There were many benefits, she said, including the possibility that it may encourage testing and entry into care. She also argued that individuals could potentially have better adherence [to treatment] than to condoms and that the synergistic effect of treatment and condom use “may be mutually reinforcing”.

She added that if successful treatment did prevent transmission it could lead to “more effective and realistic condom counselling – when you really are focusing on intensive condom use in early and late infection [when it is thought individuals are most infectious] rather than when you are on treatment.”

However, she also pointed out that there were several major caveats to this strategy including “risk compensation or behavioural disinhibition – are people going to think that if they are taking antiretroviral therapy that they need to use condoms less, even though the message is to use them both?” she asked. (It was pointed out later by a member of the audience that the message to use both condoms and treatment was not necessarily the message of the Swiss statement, but rather that of the US Centers for Disease Control and WHO/UNAIDS).

She also pointed out that “because the uninfected partner is having to rely on the infected partner telling them about their viral load, adherence and STI risks” this could “exacerbate gender imbalance in relationships” and noted that a heavy ethical burden would also fall on the HIV-positive patient’s physician.

Nevetheless, she concluded that, “it is our imperative to disseminate accurate information in order to enable an informed choice.”

Little relevance to most HIV-positive people

That was not necessarily the view of Dr Catherine Hankins, UNAIDS’ Associate Director of Strategic Information and Chief Scientific Officer who noted that “we have to be very careful about what we are saying and to whom it applies, because it can have unintended, negative consequences.”

She illustrated this by providing the example of a group of HIV-positive Geneva sex workers who believed the Swiss statement meant they did not have to use condoms, and thus could earn more money by having condomless sex.

She added that the information contained in the Swiss statement had been suppressed in an unnamed, developing country and argued that the Swiss statement – with its important caveats about knowing one's viral load and being free of an STI – was irrelevant for low and middle income countries “where 94% of all individuals live with HIV in the world today”.

She pointed out that there was extremely limited access to viral load testing in Africa and Asia and that in Africa the prevalence of STIs such as HSV-2 was extremely high, making the caveats contained in the Swiss statement unworkable. She also noted that malaria was endemic in many low and middle income countries and that since it causes a modest increase in blood plasma viral load, it may also increase genital viral load.

She said that the only possible practical application of treatment as prevention might be for fertility planning, although HIV-negative “women may need PrEP during conception” and must then return to condom use during pregnancy.

When later asked by a member of the audience why it was possible for UNAIDS to promote circumcision, when its efficacy of 60% in preventing transmission from women to men appears to be lower than the efficacy of treatment, but were “so shy” to promote treatment as prevention, Dr Hankins argued that UNAIDS was not shy. “The evidence [for circumcision] was strong,” she noted, in contrast to that for treatment as prevention.

But Professor Bernard Hirschel of University Hospital in Geneva, and one of the authors of the Swiss statement argued that “the time it takes to acquire evidence has a cost – it was 17 years between the idea that circumcision could protect men from HIV infection and conclusive evidence that this was [partially] so.”

Professor Myron Cohen had previously mentioned that a currently-enrolling international study of treatment as prevention HPTN052 would not provide its results until 2016.

Community support

Community advocate, Nikos Dedes, Chair of the Policy Working Group of the European AIDS Treatment Group (EATG), fully supported the Swiss statement and expounded its obvious benefits to individuals living with HIV. “The most important,” he said, “is the realisation that we will no longer consider ourselves to be a lifelong threat to others.”

He added that as well as allowing serodiscordant couples to have children, the statement helped to remove the fear of transmission when condoms break; helped reduce stigma and discrimination – since HIV-positive people on treatment could no longer be seen as vectors of transmission – and, more controversially, that it allowed the once-taboo subject of condomless sex to take centre stage allowing HIV-positive people to “regain the right to uninhibited experience of sexual pleasure.”

The Swiss Federal AIDS Commission themselves provided some evidence that this was the case. In a poster presentation, they reported on a brief questionnaire distributed to 185 HIV-positive individuals in several Swiss cities. Of the 134 (72%) who had heard about the statement, the vast majority expressed either a very positive (62%) or positive (26%) impact on their personal appreciation of the effect of the statement on stigmatisation.

In addition 18 of these 134 individuals changed their sexual behaviour – eleven said they now had sex without condoms with their current HIV-negative partner and seven said they now had condomless sex with their HIV-positive partner. An additional four individuals stated that they had already practised sex without condoms with their HIV-negative partner.

A further two patients said that the Swiss statement had motivated them to start antiretroviral therapy even though they currently did not have a regular sexual partner.

Many community members in the audience were vocal in their support for Nikos Dedes’ focus on the positive aspects of the Swiss statement for HIV-positive individuals, including the authors of the Mexico manifesto – amongst other things a call for “the representatives of science, medicine, economy, governments, WHO and UNAIDS” to recognise the Swiss statement and not to suppress the information.

Others, however, were concerned about the lack of evidence around the risks of anal sex, which – noted Professor Cohen – was not a practice only limited to gay men and other men who have sex with men. Dr Ulrich Marcus of the Robert Koch Institute in Berlin spoke of the “expectation and pressure” from gay HIV-positive men in Germany for the Institute to issue a similar statement to that of the Swiss, but pointed out that very high rates of STIs amongst HIV-positive gay men made it difficult for them to endorse condomless sex for this particular HIV-positive community.

Treatment marries prevention

Although there was almost as much disagreement and uncertainty amongst the audience members as there was on the panel, nearly everyone agreed that the Swiss statement had begun the vitally important process of understanding the effect of treatment on prevention.

“We need to agree how to communicate what the data show and agree on official counselling guidelines,” noted Nikos Dedes, “as well as refocus attention on STIs.”

Whatever the Swiss statement may or may not have said, the idea of treatment as a prevention tool is now “extremely important for the future,” concluded Professor Cohen, “as treatment marries prevention.”


HIV Transmission under ART. XVII International AIDS Conference, Mexico City, SUSAT41, 2008.

Wasserfallen FM Swiss statement for PLWHA on effective ARV treatment. XVII International AIDS Conference, Mexico City, abstract MOPE0212, 2008.