Minimal risk of sexual HIV transmission for heterosexual couples when the HIV positive partner has an undetectable viral load

Polly Clayden, HIV i-Base

A systematic review of publications reporting on rates of HIV transmission between heterosexual couples, where the HIV positive partner has an undetectable viral load on ART, revealed minimum risk of transmission.

Michelle Letchumanan, on behalf of researchers from Canada and Uganda, presented results at the 3rd International Workshop on Women and HIV.

The investigators searched electronic databases for all relevant observational studies and randomised controlled trials (RCTs) from 1950 to January 2012. To increase sensitivity, they reviewed the reference lists of identified studies and review articles, and conducted a hand search of selected journals to identify recently published articles that may have been missed by the literature search.

They included studies reporting HIV transmission rates, ART history and viral load of the HIV positive partner. Only three studies met all the eligibility criteria with confirmed full virologic suppression in the HIV positive partner. A further two cohort studies, and one RCT (HPTN 052) had ART and viral load data but viral suppression was unconfirmed and these and were included in a secondary analysis.

The three studies with confirmed undetectable virus reported on 991 heterosexual couples with 2,064 person-years of follow up available. The limit of detection was 50 copies/mL in one study, 500 and 50 copies/mL for another in earlier and later study periods respectively and 400 copies/mL in the third study included in this analysis.

The other three studies with unconfirmed viral suppression gave 8,170 person years of follow-up from the two observational studies reporting on 3,470 couples and the RCT reporting on 1,763 couples.

The investigators reported a transmission rate of 0 per 100-person years (95% CI: 0-0.5) for ART-treated patients when viral suppression was confirmed. The combined transmission rate when viral load was confirmed and unconfirmed was 0.14 per 100-person years (95% CI: 0.4-0.31).

Four transmissions occurred within 6 months of starting ART when viral suppression was unconfirmed. Removing these transmissions for a sensitivity analysis in compliance with the Swiss Statement criteria further reduced the upper limit of the 95%CI and yielded a transmission rate of 0 per 100-person years (95% CI: 0-0.1).

Dr Letchumanan noted that the study limitations included lack of data on: same-sex couples, type of sexual intercourse (vaginal or anal), frequency of sexual exposure, direction of transmission, viral load at the time of transmission, sexually transmitted infections rates and the extent of condom use.

But the implications for heterosexual couples are that there is a dramatically reduced minimum risk when the HIV positive partner has full viral suppression on ART, with caveats with regards to information on sexual intercourse type, STIs, and condom use.


This study has been accepted for publication PLOS One and it gives extra reassurance to couples opting for this approach and health workers providing their care.


Letchumanan M et al. Systematic review of HIV transmission between heterosexual serodiscordant couples where the HIV positive partner is fully suppressed on ART. 3rd International Workshop on HIV & Women, 14 – 15 January 2013, Toronto, Canada. Oral abstract O_04.

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