This is an excerpt from a longer article that appears in the November 19, 2018 edition of the Canadian Medical Assocation Journal.
by Jennifer LeMessurier, Gregory Traversy, Olivia Varsaneux, Makenzie Weekes, Marc T. Avey, Oscar Niragira, Robert Gervais, Gordon Guyatt and Rachel Rodin
CMAJ November 19, 2018 190 (46) E1350-E1360; DOI: https://doi.org/10.1503/cmaj.180311
Abstract
Background: The Public Health Agency of Canada reviewed sexual transmission of HIV between serodiscordant partners to support examination of the criminal justice system response to HIV nondisclosure by the Department of Justice of Canada. We sought to determine HIV transmission risk when an HIV-positive partner takes antiretroviral therapy, has a suppressed viral load or uses condoms.
Methods: We conducted an overview and systematic review update by searching MEDLINE and other databases (Jan. 1, 2007, to Mar. 13, 2017; and Nov. 1, 2012, to Apr. 27, 2017, respectively). We considered reviews and studies about absolute risk of sexual transmission of HIV between serodiscordant partners to be eligible for inclusion. We used A Measurement Tool to Assess Systematic Reviews (AMSTAR) for review quality, Quality in Prognosis Studies (QUIPS) instrument for study risk of bias and then the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence across studies. We calculated HIV incidence per 100 person-years with 95% confidence intervals (CIs). We assigned risk categories according to potential for and evidence of HIV transmission.
Results: We identified 12 reviews. We selected 1 review to estimate risk of HIV transmission for condom use without antiretroviral therapy (1.14 transmissions/100 person-years, 95% CI 0.56–2.04; low risk). We identified 11 studies with 23 transmissions over 10 511 person-years with antiretroviral therapy (0.22 transmissions/ 100 person-years, 95% CI 0.14–0.33; low risk). We found no transmissions with antiretroviral therapy and a viral load of less than 200 copies/mL across consecutive measurements 4 to 6 months apart (0.00 transmissions/100 person-years, 95% CI 0.00–0.28; negligible risk regardless of condom use).
Interpretation: Based on high-quality evidence, there is a negligible risk of sexual transmission of HIV when an HIV-positive sex partner adheres to antiretroviral therapy and maintains a suppressed viral load of less than 200 copies/mL measured every 4 to 6 months. Sexual transmissions of HIV have occurred when viral load was more than 200 copies/mL with antiretroviral therapy or condoms alone were used, although the risk remains low. These findings will help to support patient and clinician decision-making, affect public health case management and contact tracing, and inform justice system responses to HIV nondisclosure.
In Canada, an estimated 82% of people living with HIV acquired their infection through sexual transmission. Under current Canadian criminal law, people can be prosecuted for not disclosing their HIV-positive status when they engage in sexual activity that poses a “realistic possibility” of HIV transmission.
Based on high-quality evidence, there is a negligible risk of sexual transmission of HIV when an HIV-positive sex partner adheres to antiretroviral therapy and maintains a suppressed viral load of less than 200 copies/mL measured every 4 to 6 months.
Previous reviews have shown that both antiretroviral therapy and condoms reduce the possibility of HIV transmission. Antiretroviral therapy inhibits viral replication with the goal of suppressing viral load to an undetectable level, defined as a plasma HIV-1 RNA level below 20–50 copies/mL. In 2016, an estimated 86% of the 63 110 people living with HIV in Canada were aware of their infection, 81% of those diagnosed were taking antiretroviral therapy and 91% of those being treated had a suppressed viral load of less than 200 copies/mL. Although previous reviews have shown the preventive benefit of antiretroviral therapy, use of condoms or both, they have not included the most recent studies that have changed clinical guidance and public messaging, and could affect Canadian criminal law.
To support the examination of the criminal justice system’s response to HIV nondisclosure by the Department of Justice Canada, we synthesized evidence on the absolute risk of HIV transmission during sex between serodiscordant partners. Our objectives were to determine risk when a sex partner who is HIV-positive (Q1) is taking antiretroviral therapy (with varying levels of viral load); (Q2) is taking antiretroviral therapy and has a suppressed viral load; (Q3) is taking antiretroviral therapy and either partner uses condoms (or other barrier methods); (Q4) is taking antiretroviral therapy and has a suppressed viral load, and either partner uses condoms (or other barrier methods); and when (Q5) either partner uses condoms (or barrier methods) alone.
The Public Health Agency of Canada, in consultation with the Department of Justice Canada, chose these questions and the outcome of interest (absolute risk of HIV transmission) as most relevant to informing public health and legal responses.
Read the complete piece in the Canadian Medical Association Journal