Viral Suppression Effective for Reducing HIV Transmission Among Men

HIV electron microscope
HIV electron microscope
Investigators aimed to assess the risk for HIV transmission in serodiscordant male homosexual couples, focusing on times when couples reported condomless anal intercourse.

For HIV-positive men who have sex with men, viral suppression through HIV treatment effectively helps prevent transmission, according to results published in The Lancet.

These results indicate that increasing the rate of HIV testing and immediate treatment are key prevention tactics for men who have sex with men.

The study included serodiscordant male homosexual couples from 13 clinics in Australia, 1 in Brazil, and 1 in Thailand. HIV-negative participants provided information on sexual behavior and were tested for HIV and sexually transmitted infections at study visits. HIV-positive participants underwent viral load tests, CD4 cell count, and sexually transmitted infections tests. The researchers defined viral suppression at <200 copies/mL. They used phylogenetic analysis to identify HIV transmission and calculated incidence per couple-year of follow-up.

Overall, 343 couples were enrolled for 588.4 couple-years from May 8, 2012, to March 31, 2016, in Australia and May 7, 2014, to March 31, 2016, in Brazil and Thailand.

Of the couples, 75% (n=258) of HIV-positive partners had viral loads that were consistently <200 copies/mL. Daily pre-exposure prophylaxis was used among 34% (n=115) of HIV-negative partners during follow-up.

During the follow-up period, 74% (n=253) of couples reported within-couple condomless anal intercourse for a total of 16,800 acts.

New HIV infections occurred in 3 cases, but none were phylogenetically linked. For these infections, there were 232.2 couple-years of follow-up, 12,447 condomless anal intercourse acts during periods when HIV-positive partners had viral suppression and HIV-negative partners did not use pre-exposure prophylaxis, representing an upper confidence interval limit transmission rate of 1.59 per 100 couple-years of follow-up.

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“This study provides evidence that HIV transmission in the context of viral suppression is very low, although we cannot exclude higher levels of risk based on the upper [confidence interval] limit,” the researchers wrote.


Bavinton BR, Pinto AN, Phanuphak N, et al. Viral suppression and HIV transmission in serodiscordant male couples: an international, prospective, observational, cohort study [published online July 16, 2018]. Lancet. doi:10.1016/S2352-3018(18)30132-2