Only low risk of HIV transmission among those well controlled on antiretroviral therapy

1. This prospective study found no instances of HIV transmission among serodiscordant couples engaging in condomless sexual intercourse when the HIV-infected partner was taking antiretroviral therapy and maintaining a viral load below 200 copies/mL.

2. The calculated upper limit of HIV transmission risk in these couples is 0.3 per 100 couple-years overall, and 0.71 per 100 couple-years for anal intercourse.

Evidence Rating Level: 2 (Good)

Study Rundown: It has been long established that HIV-infection can be spread primarily by sexual contact, among other routes. Previous studies have shown that the use of antiretroviral therapy (ART) can reduce the rate of transmission by as much as 96%. Therefore, the World Health Organization has recommended the widespread use of ART in all HIV-infected patients, regardless of CD4 count, in an effort to stem the spread of disease. However, much of the data used to support this guideline have come from studies in which couples have reported diligent condom use. Thus, to determine the effectiveness of this recommendation in a broader population, the Partners of People on ART – A New Evaluation of the Risks (PARTNER) study sought to determine the rate of transmission in couples reporting condomless intercourse. This study followed a large number of serodiscordant couples that engaged in condomless sex in which the HIV-infected partner was taking ART and maintained a viral load below 200 copies/mL. It found a transmission rate of 0% for all forms of sex. The upper confidence limit of transmission was calculated to be 0.3/100 couple-years overall, and 0.71/100 couple-years for anal penetrative sex.

This study shows that the rate of HIV transmission is low among serodiscordant couples in which the HIV-infected partner is well controlled on ART. However, it was not designed to estimate the risk of transmission at different points of infection and was conducted with only a minimal duration of follow-up. Thus, longer-term studies are needed to provide more precise temporal estimates of risk.

Click to read the study in JAMA

Relevant Reading: Viral load and heterosexual transmission of Human Immunodeficiency Virus type 1

In-Depth [prospective cohort]: The PARTNER trial observed a total of 1166 HIV serodiscordant couples from 14 different countries who reported condomless sexual intercourse between September 2010 and May 2014. Couples were eligible for enrollment as long as the HIV-infected partner was taking suppressive ART and their HIV-1 RNA load remained less than 200 copies/mL. A total of 888 couples (548 heterosexual, 340 MSM) reported information over a mean follow-up of 1.3 years. Couples that contributed data tended to be older, engage in longer durations of condomless sex, and have higher CD4 counts on average. During follow-up couples engaged in condomless sex 37 times per year on average. By the end of the study period, 11 total HIV-negative partners became infected (10 MSM, 1 heterosexual, 8 reported condomless sex with partners outside of their studied relationship), however, no transmission of phylogenetically linked virus occurred. Thus, the overall rate of within-couple HIV transmission was reported as 0 (transmission rate 95% CI 0 to 0.3/100 couple-years of follow-up). The transmission rate for anal intercourse was also 0 with a 95% upper-limit of approximately 0.71/100 couple-years of follow up.

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