Treatment as prevention

Treatment as prevention of HIV

19-05-2011 – Last week the United States National Institutes of Health announced results that a large randomised study of treatment as prevention, the HPTN 052 trial, showed that antiretroviral therapy reduces the risk of HIV transmission in couples where one partner has HIV by 96%.

Ard van Sighem, senior researcher at SHM comments: "There was already awareness that treatment of HIV can prevent new infections. It's been known for quite a while that the risk of infection from an infected partner is related to the amount of virus RNA present in the blood of the infected patient. The higher the number of virus particles per millilitre blood, the greater the chance of infection. With very low amounts of virus RNA in the blood, which is often the case with effective antiviral treatment, the chance of infecting an uninfected partner is negligible."

So although the knowledge that therapy helps to prevent new infections is nothing new, Dr. van Sighem acknowledges that this may be a useful prevention technique in long-term partnerships. "For many reasons, consistent condom use in long-term partnerships may be difficult. Treatment of the infected partner is then a possible solution."

In the Netherlands, however, this study has little relevance for a number of reasons. "In the study, infected persons had CD4 cell counts between 350 and 500 cells per cubic millimetre at the time of enrolment. That is high in relation to the Netherlands where almost half of the people have less than 350 cells/mm3 at the time of diagnosis. Regular testing is of great importance. In the Netherlands, not enough of the group that are at risk of infection are tested every year. Treatment can only be started once there is a positive diagnosis. If diagnosis of infection occurs late, then there is a chance that the partner is already infected."

"And you have to realise that the use of antiretroviral therapy is not to be underestimated. Patients must use medication every day for the rest of their lives without interruption. And there can be side effects, so any possible delay in starting treatment is welcome. Starting treatment earlier than currently recommended, however, does seem to have other benefits for the HIV-infected patient himself apart from preventing transmission of HIV to uninfected partners. The ultimate decision of when to start therapy should, however, remain the choice of the HIV-infected person."

Furthermore, "This study is primarily in heterosexual couples, while the HIV epidemic in the Netherlands is mostly amongst homosexual men. The results of this study can't be directly transferred from one group to the other. What is necessary is a similar large-scale study in homosexual men. In the Netherlands, it seems that around 90% of the new HIV infections in homosexual men are transmitted from men that are unaware of their infection, because they haven't been tested, and are therefore not receiving treatment."

"The study has also shown that approximately a fifth of the HIV infections (7 of the 39 infections, with another 4 still undergoing analysis) were transmitted via a partner other than the treated steady partner. This means that although the infected partner is treated, the uninfected partner is still susceptible to infection from another infected sexual partner."

"One of the potential problems with therapy as prevention is that condoms will not be used anymore. If the therapy doesn't work properly, due to irregular use or the HIV virus developing resistance to a medication, then the virus RNA amount remains high in the blood, as does the risk of transmission. Frequent monitoring of RNA levels is therefore crucial."

The WHO and UNAIDS press release comments that no single method is fully protective against HIV. Treatment for Prevention needs to be used in combination with other HIV prevention options. However, the significance of the research trial findings makes Treatment for Prevention an integral part of the HIV prevention package.

Further information: 

• HPTN 052, A Randomized Trial to Evaluate the Effectiveness of Antiretroviral Therapy Plus HIV Primary Care versus HIV Primary Care Alone to Prevent the Sexual Transmission of HIV-1 in Serodiscordant Couples. Link to website
• NIH News Release, 12 May 2011 : Treating HIV-infected People with Antiretrovirals Protects Partners from Infection. Link to release
• Estimating the risk of HIV transmission from homosexual men receiving treatment to their HIV-uninfected partners. Hallett TB, Smit C, Garnett GP, de Wolf F. Sex Transm Infect. 2010 Jul 18. [Epub ahead of print] Link to publication
• WHO/UNAIDS Press Release,12 May 2011: Groundbreaking trial results confirm HIV treatment prevents transmission of HIV. Link to release