Undetectable viral load associated with unprotected sex amongst gay men in Sydney

Michael Carter
Published: 23 July 2004

In gay couples where one partner is HIV-positive and the other HIV-negative, an undetectable viral load is associated with unprotected anal sex, according to a study conducted in Sydney and presented as a poster to the Fifteenth International AIDS Conference in Bangkok last week.

This finding adds further weight to a recently published meta-analysis of studies looking at the association between HIV treatment and sexual risk taking. This meta-analysis, which was reported on aidsmap.com found that although the use of HAART in itself was not associated with unprotected sex, a belief that HAART or an undetectable viral load made HIV less infectious was associated with unprotected sex.

Investigators in Sydney wished to see if in gay couples where one partner was HIV-positive and the other HIV-negative, an understanding that the HIV-positive man’s viral load was undetectable was associated with unprotected anal sex.

Data were collected from gay men involved in two ongoing cohort studies in Sydney. HIV-negative men were recruited from the Health in Men cohort between late 2001 and late 2003, and HIV-positive men from the Positive Health cohort between early 2002 and the summer of 2003.

As well as supplying information about whether or not they had unprotected anal sex, men recruited to the study were also asked to complete an HIV optimism questionnaire.

A total of 119 couples, where one partner was HIV-positive and the other HIV-negative, were recruited to the study. In total 20% of couples did not have any anal sex, and 68.9% of couples did not have unprotected anal sex. However, in 10.1% couples (26 individuals) unprotected anal sex did occur. The investigators found that unprotected anal sex was significantly more likely to happen in relationships when the HIV-positive man’s viral load was understood to be undetectable (p = 0.04).

Investigators then undertook further analysis to see if age and HIV optimism were associated with unprotected anal sex in couples where the HIV-positive man had an undetectable viral load.

They found that although both age (p = 0.004) and HIV optimism (p = 0.03) were associated with unprotected anal sex, an undetectable viral load remained a significant predictor of unprotected anal sex (p = 0.04).

However, the investigators found that even when unprotected anal sex was occurring, men in serodiscordant relationships were making efforts to minimise the risk of HIV transmission. Of the 15 HIV-negative men, eleven (73.3%) reported never having unprotected receptive anal sex with their partner, and of the eleven HIV-positive men, eight (72.7%) said they never ejaculated inside their HIV-negative partner when having unprotected insertive anal sex.

In their conclusion, the investigators stress that most serodiscordant gay couples in Sydney do not engage in unprotected anal sex. However, when unprotected anal sex does occur in serodiscordant couples it is significantly associated with an undetectable viral load in the HIV-positive partner, younger age, and optimism about HIV. Even when unprotected sex does occur, men often make efforts to minimise the risk of HIV transmission, for example by withdrawal before ejaculation if the HIV-positive partner is the insertive partner.


Van de Ven P et al. Undetectable viral load associated with more unprotected anal intercourse in serodiscordant gay couples in Sydney. XV International AIDS Conference, Bangkok. Poster presentation, abstract TuPeD5160, 2004.

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