ART use doesn't increase sexual risk among people with HIV in the UK

Taking antiretroviral therapy (ART) is not associated with an increased risk of condomless sex with HIV-negative/unknown status partners – sex that potentially involves a risk of transmission  – investigators from the UK report in the online edition of AIDS. Moreover, ART was associated with a significant reduction in the prevalence of sex involving a risk of HIV transmission.

“In this large multicentre study of people attending HIV clinics in the UK in 2011/12, use of ART was not associated with higher prevalence of CLS-D [condomless discordant sex],” comment the authors.

HIV transmission rates in the UK continue to be high, especially among men who have sex with men (MSM). Although it has been estimated that most new HIV infections have their source in individuals who are unaware they have HIV, a significant proportion – up to 20% in MSM – arise from people who are already diagnosed.

There is now convincing evidence that people taking ART who have an undetectable viral load are extremely unlikely to pass HIV on to their sexual partners. The health benefits of prompt ART have also been established, and most treatment guidelines therefore now recommend the early initiation of HIV therapy.

It is uncertain if taking ART influences sexual behaviour, especially when viral load is suppressed. Investigators from the UK therefore designed the ASTRA (Antiretovirals, Sexual Transmission Risk and Attitudes) study to see if ART and perceived viral load status had an impact on sexual behaviour, especially condomless sex with a partner who was HIV-negative or of unknown HIV status.

Eight hospital HIV outpatient clinics across the UK participated in the study, recruiting 3178 adult patients (of which 88% were taking antiretroviral therapy), all of whom had diagnosed HIV infection for at least three months.

Participants were asked to complete a questionnaire about their demographic background, use of ART, perceived viral load and sexual behaviour in the previous three months. In particular, participants were asked whether they had had condomless anal or vaginal sex with a partner who was HIV-negative/unknown status. MSM were asked if they were receptive, insertive, or both, and if insertive, if they ejaculated in their partner.

Participants were also asked whether they believed that an undetectable viral load made someone less infectious, and whether people with an undetectable viral load needed to use condoms to prevent HIV transmission.

The study population comprised 2189 MSM, 360 heterosexual men and 629 women. The vast majority reported being on ART, including 87% of MSM, 93% of heterosexual men and 89% of heterosexual women, of whom 84%, 62% and 71%, respectively, had an undetectable viral load.

Analysis of the sexual behaviour of MSM showed that 38% reported condomless sex, with 15% reporting condomless sex with an HIV-negative/unknown partner. Of men in the latter category, less than a third reporting insertive sex ejaculated in their partner and 40% said they only had receptive anal sex. MSM reporting condomless sex with HIV-negative/unknown partners were more likely than other MSM to report sexually transmitted infections (22 vs 9%) and group sex (45 vs 16%).

Overall MSM on ART were less likely to report condomless sex with HIV-negative/unknown partners than men who were not on ART (14 vs 19%, p < 0.05). Those on ART were also less likely to report sexually transmitted infections (10 vs 17%), group sex (20 vs 29%) and ten or more partners in the past year (25 vs 36%) – all p < 0.001.

Among MSM on ART, prevalence of condomless sex with HIV-negative/unknown partners was higher among those reporting an undetectable viral load than those reporting a viral load above 50 copies/ml (15 vs 10%, p = 0.014). However, prevalence of condomless sex with a possible risk of HIV transmission was higher among MSM not on ART (19%) than in both ART groups.

After taking into account demographic and HIV-related factors, compared to MSM on ART reporting an undetectable viral load, those on ART without an undetectable viral load has a significantly lower prevalence of condomless sex with HIV-negative/unknown partners (adjusted PR = 0.67; 95% CI, 0.46-0.96).

Answers provided by heterosexual men and women showed that 6% and 11%, respectively, reported condomless anal/vaginal sex with HIV-negative/unknown partners.

Among heterosexual men, prevalence of condomless anal/vaginal sex with HIV-negative/unknown partners did not differ significantly between those on ART and those not on ART (6 vs 4%), a finding replicated in heterosexual women (11 vs 9%).

The majority of participants believed that condoms were needed to prevent HIV transmission, even in the context of an undetectable viral load. However, just over a third (38%) of participants reporting condomless sex with HIV-negative/unknown partners gave “belief that transmission risk is very low” as one reason for not using a condom. The percentage was 42% for those reporting an undetectable viral load, 23% for people on ART with a detectable viral load and 28% for people not on ART.

A check of clinic records showed that 97% of participants reporting an undetectable viral load did in fact have a viral load below 50 copies/ml.

“These results highlight the importance, as ART use expands, of promoting sustained high adherence, regular viral load testing, and ongoing awareness of personal viral load,” comment the researchers.

Prevalence of risk of HIV transmission was 3% overall: 16% among those not on ART, 3% for patients on ART with a detectable viral load, and 0.6% for ART-treated patients with viral suppression.

“Among people with HIV in the UK, use of ART was not associated with increased prevalence of CLS [condomless sex] or CLS-D [condomless discordant sex], and was associated with greatly reduced prevalence of [HIV transmission] risk,” conclude the researchers. “These results support the prevention role of ART offered to all people with HIV, and emphasise the need to focus on HIV/STI prevention among those not wishing to start ART.”