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Zero HIV transmission risk uncertain in serodiscordant couples with ART
Findings from a systematic review suggest that the available data do not support a zero risk for HIV transmission among heterosexual serodiscordant couples when the positive partner is receiving antiretroviral therapy.
“This is in contradiction with the statement from the Swiss Commission on AIDS which asserted in 2008 that people with HIV on effective ART for at least 6 months and without other sexually-transmitted infections cannot transmit HIV through unprotected sex,” researchers Virginie Supervie, PhD, of INSERM in Paris, and Romulus Breban, PhD, of the Institut Pasteur in Paris, told Infectious Disease News. “Current data support only that the risk of HIV transmission is below 13:100,000. It would require collecting 12 times the amount of available data without observing any HIV transmission to be able to say that the risk is below 1:100,000, as specified in the Swiss Statement.”
The review included six studies that examined HIV transmission among serodiscordant, heterosexual couples, in which the positive partner was on ART. The studies had information on incident HIV infections among the negative partners, the viral loads of the treated partner, condom use and sexual activity.
Among the 1,672 couples, there were four incident HIV transmissions that were genetically linked to the index partner. Three of the transmissions occurred when the index partner had been receiving ART for less than 6 months. The fourth occurred within the first year of ART treatment, but the data were insufficient to determine whether the infection occurred before or after 6 months of ART. The median number of sexual acts per couple was three to 12 per month and condom use was high.
There were an estimated 113,480 sex acts that occurred when the index partner had received ART for at least 6 month, and 17% were not condom-protected. The researchers estimated the upper-bound of the per-act risk of HIV transmission after 6 months of ART in a Bayesian analysis and found it to be 8.7:100,000 or 13:100,000, depending on whether no infection or one infection occurred after 6 months of ART. The data suggested that to estimate the upper-bound per-act risk of 1:100,000, more than 326,000 condom-unprotected sex acts need to be monitored.
Supervie and Breban said that they are currently updating their data to take into account the data from the PARTNER study, which reported zero infections during an estimated 28,023 sex acts between heterosexual serodiscordant couples where the HIV-positive partner is virally suppressed. They said it will lower the upper bound estimate for the risk of HIV transmission, but will not be enough to lower it to below 1:100,000.
“The risk of transmission is small, but the risk cumulates with the number of exposures and may represent a long-term concern,” Supervie and Breban said. “Combining ART with other prevention methods may provide optimal protection against HIV transmission.” — by Emily Shafer
Disclosure: The researchers report no relevant financial disclosures.