Antiretroviral treatment reduced the risk of HIV transmission by 77% in serodiscordant couples in rural South Africa, a population-based study carried out in the province of KwaZulu-Natal has shown. The findings are published in advance online in Clinical Infectious Diseases.
The investigators say that their findings provide a real-life estimate of the impact of antiretroviral treatment on HIV transmission under normal community conditions.
The study findings come from a longitudinal population-based study that is being conducted in northern KwaZulu-Natal province by the Africa Centre for Population Health. KwaZulu-Natal has the highest prevalence of HIV in South Africa (29%) and HIV incidence remains high. Antiretroviral treatment began to be provided in the province in 2004.
The investigators set out to establish whether HIV transmission was being reduced by antiretroviral therapy in the KwaZulu-Natal setting, and whether this reduction matched the impact of antiretroviral therapy on transmission in serodiscordant couples in the HPTN 052 randomised clinical trial. In the carefully monitored conditions of the HPTN 052 trial, where 89% of participants were virally suppressed, antiretroviral therapy reduced transmission by 96%.
The analysis looked at the effect of antiretroviral treatment on HIV transmission in serodiscordant couples between 2005 and 2013. The analysis looked at both cohabiting and non-cohabiting couples. The researchers identified cohabiting couples via demographic household surveillance and ascertained HIV status data from surveillance data. Non-cohabiting couples were identified by self-report.
The outcome of interest was HIV seroconversion during longitudinal follow-up in previously HIV-negative partners of HIV-positive individuals. HIV-negative individuals ceased being followed if the cohabiting relationship ended. Antiretroviral treatment status of HIV-positive individuals was ascertained from the records of the Hlabisa HIV Treatment and Care Programme, which provides free access to antiretroviral treatment at 17 primary health care clinics in the district.
Participants in the study were being tested regularly for HIV during the follow-up period as part of the larger longitudinal population study, on average around once a year (median interval 374 days interval between tests).
A total of 17,106 adult individuals contributed 60,349 person-years of follow-up. The study identified 2029 HIV-negative people with a cohabiting partner, of whom 196 had a partner with HIV infection. The remainder had HIV-negative partners. Of the 196 partners with HIV, 20 were on antiretroviral treatment at baseline and a further 56 began treatment during the follow-up period.
Sixty-three per cent of participants were women. The median age of participants was 33 years but the median age was substantially higher in women than in men (36 years vs 28.5 years). Just over three per cent (3.3%) of participants reported having more than one sexual partner in the previous 12 months; men reported multiple partners more frequently than women (7.2% vs 0.6%). Inconsistent condom use was reported by 37.4% of participants and was more commonly reported by women (42.9% vs 29.1%).
Participants in the study were being tested regularly for HIV during the follow-up period as part of the larger longitudinal population study, on average around once a year (median interval 374 days interval between tests).
Incidence was highest among people with an HIV-positive partner not on antiretroviral therapy (5.6 per 100 person-years of follow up, 95% CI 3.5-8.4), compared to 1.4 per 100 person-years (95% CI 0.4-3.5) in people with an HIV-positive partner on therapy. Having a partner who was taking antiretroviral treatment reduced the risk of acquiring HIV by 77% (HR 0.23, 95% CI 0.07-0.80).
The investigators point out that drug stockouts and missed clinic appointments were common at the primary health care clinics providing antiretroviral treatment to the population who took part in the study, suggesting that viral suppression may have been less than perfect among those on treatment. Province-wide viral suppression among people receiving antiretroviral therapy prior to 2010 had been reported as 77%.
Among people with HIV-negative partners HIV incidence was 0.3 per 100 person-years (95% CI, 0.2–0.5) and among people who reported not being in a relationship incidence was 3.2 per 100 person-years (95% CI 3.1-3.4).
Overall incidence in the study population was 2.7 infections per 100 person-years, compared to a maximum observed incidence of 6 infections per 100 person-years in young women in the province previously reported by the Africa Centre research group in the same rural population. These findings suggest the very substantial role played by ongoing rather than casual partnerships in HIV transmission in the district, and the need for both improved awareness of HIV status and supported disclosure. Only 29% of participants were previously aware of their HIV status at the time they were first tested, and whereas in the HPTN 052 study all participants with HIV had disclosed their HIV status to partners, in this study population disclosure was an individual decision.
Both multiple partnerships and inconsistent condom use were found to be independently associated with HIV acquisition.
The investigators caution that their findings may not be generalisable to settings where the age structure is substantially different, for example where serodiscordant partnerships are more prevalent among younger people.
Although a 77% reduction in HIV transmission is encouraging, it is important to note that the incidence rate recorded among partners of people on antiretroviral therapy was 1.4 infections per 100 person-years of follow up. In a setting with very high incidence, such as KwaZulu-Natal, “additional prevention interventions will likely be required to eliminate HIV transmission in serodiscordant couples,” the authors conclude.
It is also important to note that viral suppression in this community sample may have been considerably lower than in the HPTN 052 study population, emphasising the importance of maximising retention in care, minimising drug stockouts and ensuring that people collect medication before previous prescriptions run out. Community-based interventions that improve retention and support adherence are likely to pay dividends in improving viral suppression and reducing HIV transmission.
References
Oldenburg C et al. Antiretroviral therapy to prevent HIV acquisition in serodiscordant couples in a hyperendemic community in rural South Africa. Clin Infect Dis, advance online publication, 20 May 2016.