Spotlight Center on HIV Prevention Today


HIV Undetectable Does Equal Uninfectious: The Swiss Statement and the Vindication of Pietro Vernazza

October 7, 2016

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Show Me the Data

Kalichman remembers where he was when he saw the Swiss Statement that January in 2008. He was in his office at the University of Connecticut, where he does behavioral research on people living with HIV who also use drugs or have multiple partners. He said he grabbed his desk phone and dialed up the World Health Organization (WHO).

"What do you think is going on here?" he remembered asking them.

Kalichman, a 2005 Distinguished Scientist from the Society for Behavioral Medicine, just knew it would be misinterpreted by the masses.

And he wasn't the only one. Public health agencies including WHO, UNAIDS and those in France and Australia roundly rejected the Swiss Statement. Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Disease (NIAID) at the National Institutes of Health (NIH) told TIME magazine that he, WHO, and the CDC were "concerned" about telling people that there was no risk.

"There is no such thing," he told the magazine, "as zero risk."


By the time the International AIDS Conference rolled around in July that year, the statement had become the subject of a special panel discussion at which Vernazza answered the questions of several scientists, among them his old UNC mentor, Mike Cohen. At the two-hour event, Vernazza apologized for the statement's misleading headline ("HIV-positive people with no other STIs and on effective antiretroviral therapy do not transmit HIV sexually"), saying he would have said that people living with HIV have "very little" chance of transmitting HIV rather than "do not" transmit it. He added that the statement was never meant to influence global policy; it was intended to guide Swiss doctors, only, in discussing sexual risk with their patients.

Individual researchers also reacted. Some, such as Sharon Hillier, Ph.D., a microbiologist at the University of Pittsburgh and a member of the program committee of the HIV Research for Prevention conference, said her first reaction to the statement was, "Yes, of course."

"To be quite honest, as a biologist, you think, 'If you're fully suppressed you can't transmit the virus,'" she said. "And so, to me, it's just logical. I didn't think it was some blinding breakthrough."

But not everyone was so sanguine.

"Being a scientist, you scrutinize, 'What is the data in support of that statement, that you essentially become non-infectious if placed on treatment?'" said Jens Lundgren, M.D., DMS.c, professor of infectious diseases and founder of the Centre for Health and Infectious Disease Research at the University of Copenhagen. "We need to separate out our personal feelings from the process of doing research, because the research has to be objective and has to be looking at both ends of the question. Therefore, opinions should be derived from the research results. You should be very concerned if you're building too strong an opinion before the research is done."

The Swiss Statement, he said, "was an opinion based on plausible but weak data."

UNC's Cohen agreed, saying he worried that a few observational studies, a mathematical model and Vernazza's clinical experience weren't enough to call for policy change.

"Policy decisions depend on high levels of evidence," Cohen told "The Swiss Statement was a giant piece of deductive logic."

Others had even stronger reactions. Vernazza said at least one researcher stopped talking to him after the statement came out.

Despite the blowback, Vernazza said arguments against the Swiss Statement only bolstered his belief that he was right about transmission and infectiousness. But more than that, he said, his patients couldn't wait for the clinical trials to be completed if they wanted to have children.

"I was saying in 2008 that it will take eight years to show that we were right," he said recently. "I do not agree that we should let patients wait for this relief. And now, look -- it took eight years."

Getting the Data

One thing that's true about HIV researchers is that they fight about issues for years -- and that fight only ends when the data is in.

Take immediate versus delayed antiretroviral therapy.

"It was a huge controversy," said Lundgren. "There were strong emotions."

The emotions and shouting only cooled last year, he said, when data from the START trial proved that early testing and treatment were better for everyone.

So the fact that there were vigorous debates, even fights, about the Swiss Statement isn't a problem. It's an incitement to research.

"The only thing I know to do when I see things like this is to generate research that either refutes or supports the statement," Lundgren said. "That's what we did."

Indeed, Lundgren worked with a team of researchers, including Vernazza, on the PARTNER study, a study that followed a group of straight and gay people living with HIV and on suppressive antiretroviral therapy and their HIV-negative partners as they had condomless sex to see whether treatment really did prevent transmission.

For the scientists involved in another study called HPTN 052, the Swiss Statement didn't influence their research -- they'd begun planning the international, randomized controlled trial of HIV treatment and prevention in 2000. But it did have a big impact on it, said Mike Cohen, HPTN 052's principal investigator.

"I'll say this about the Swiss Statement," Cohen said. "It shined a light on 052."

So when the early results of HPTN 052, which followed 1,763 HIV-positive people around the world and their partners, were unblinded in 2011, they were the first concrete facts on the power of treatment to reduce transmission. And boy, did they reduce transmission: In 1.7 years, only one new HIV acquisition could be linked directly to a partner on antiretroviral therapy. For people not yet on treatment, there were 27 new linked HIV transmissions.

That's a 96% drop in infectiousness. (But that doesn't mean that someone on suppressive antiretroviral therapy has a 4% chance of passing on the virus. The initial study didn't investigate whether the person whose partner acquired HIV from them had a suppressed viral load; that came later.)

Unlike Vernazza, who had total confidence in the power of treatment to reduce transmission, Cohen had not been as sure what his study would find. There's a myth, he said, that the 052 team was confident from the start. Not so, he said -- not at all.

"My colleague Marybeth [McCauley] was literally shaking [when it became clear that the study's oversight board was going to make a recommendation that would affect the future of the study, in 2011]," he said. "We absolutely thought the study had failed."

But it hadn't. That year, Science named HPTN 052 its Breakthrough of the Year.

That was followed, in 2014, by the preliminary results of the PARTNER study, which reported similarly spectacular outcomes. Out of 48,000 instances of condomless sex between people on suppressive antiretroviral therapy and their HIV-negative partners, there was not a single linked case of HIV. That means that, if people did acquire HIV, it was genetically different enough from their partners' virus to indicate that they got it from someone else.

This was particularly important because PARTNER, unlike HPTN 052, only studied condomless sex, not HIV transmission with condom use. More than 90% of the couples in HPTN 052 reported that they used condoms, leading some researchers, including Lundgren, to say that the benefit of treatment for reducing transmission was probably even higher. Plus, PARTNER included a large number of gay couples, showing that treatment also prevents transmission via anal sex.

Then, to top off this series of positive results, Cohen's team reported out the final results of HPTN 052 in July 2015. They were even better than the preliminary results: Of the new cases of HIV in the study, all were linked to people who'd been on treatment for less than six months or who hadn't yet started treatment -- in other words, to people who didn't meet the Swiss Statement criteria.

"The real point, to us, is that because of the results of 052 and PARTNER's work with gay couples, it becomes increasingly compelling," Cohen said, "that if people are sufficiently suppressed, transmission becomes exceedingly rare."

Lundgren agreed.

"The data," he said, "support strongly that the Swiss Statement is correct."

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This article was provided by TheBody.

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