HIV prevalence in Bloemfontein's Free State Province has been close to 30% in antenatal surveillance for several years. Prevalence was lower in this study, at 21.2%, yet we detected a high incidence rate of 5.5/100 PY in the overall cohort. We observed similar HIV incidence across the age spectrum in the Bloemfontein cohort, contrary to national estimates.8
The HIV prevalence among Rustenburg women in the cross-sectional screening was 23.5%, again lower than recent antenatal surveillance data from the area, which could be explained by the young average age of the cohort screened. The prospective incidence rate in the Rustenburg cohort was 3.0/100 PY and higher among younger women (4.0/100 PY in 18–24 year olds).
National household survey data in South Africa show that HIV prevalence has stabilised and suggest that the incidence estimated from nationally representative surveys has declined in younger age groups.8
But the overall estimated incidence remained 1.3/100 uninfected persons of reproductive age from 2005 to 2008.8
Others have described a pattern of stable prevalence in South African antenatal surveillance and population-based surveys coupled with substantial incidence rates in defined cohorts.9
In the relatively few studies that have directly measured HIV incidence, it has been distressingly high in both urban and rural sites, despite multiple follow-up contacts, ongoing risk-reduction counselling and condom promotion and provision. Between 2001 and 2004, a representative cohort in one part of rural Limpopo Province had an HIV incidence of 4.9/100 PY among women, despite self-reported increases in condom use during that period.10
In the HPTN 055 cohort study, the two South African sites, both located in Kwa-Zulu Natal Province, had the highest HIV incidence rates in 2003–2004 (Durban 5.3/100 PY and Hlabisa 6.2/100 PY).11
In 2004–2007, the HIV incidence rate was 6.4/100 PY and 6.5/100 PY in an urban and a rural cohort in KwaZulu-Natal, respectively.9
Three recent randomised trials of ineffective prevention products have also reported substantial HIV incidence at their South African sites.12–14
Finally, a cohort study conducted between 2007 and 2009 at two sites in Northwest Province and Western Cape Province for capacity-building purposes reported 12-month incidence rates of 6.0/100 PY and 4.5/100 PY, similar to the rates reported here.15
Older participants had a higher risk of prevalent HIV infection in our study than younger, reflecting their longer potential for exposure to HIV. Lesser education was also associated with baseline HIV infection, as has been found in other South African studies.10
Other factors were not consistently associated with baseline infection across the sites, which may stem from unmeasured sexual network factors and misclassification error resulting from self-report. In fact, the striking differences in the self-reported risk behaviours between these two cohorts suggest that some self-reporting bias may have occurred. Bloemfontein participants reported high rates of multiple partnering (about two-thirds of the women) compared with national data on South African women aged 15–49 years (3.7% in 2008) and data on men and women in the Free State in the same 2008 survey (14.6%).17
In contrast, reports of multiple partnering at the Rustenburg site were close to national averages (12%–14%) and similar to a prior representative household survey in Rustenburg.18
One weakness of our analysis is that, partly due to the relatively short follow-up period, there were too few seroconversion events to do multivariable proportional hazards regression, and our univariate regression results for incident HIV infections were necessarily inconclusive. A limitation of the analysis of risk factors for prevalent HIV infections is that the behaviours reported at screening may not have reflected behaviours present at the time of infection. Lack of STI diagnostic testing precluded evaluating associations with other infections.
Perhaps the greatest study weakness relates to the validity of self-reported sexual behaviours, both for purposes of determining eligibility as well as for assessing risk during follow-up. The inaccuracies in self-reported sexual behaviour during research interviews have been amply documented and are not unique to these studies. Although we attempted to keep the eligibility factors secret from participants and outreach staff, we do not know if volunteers (both eligible and ineligible) guessed those factors and shared them with other women in the community. There may have been an awareness among women at the Bloemfontein site in particular to over-report risky behaviours to gain entry to the study: the eligibility rate was very high there and risk behaviours far exceeded national estimates. Alternatively, recruiters at the Bloemfontein, but not the Rustenburg, site may have simply tapped into a subgroup of women with particularly risky behaviour. During baseline and follow-up interviews with participants, however, we did not observe strong associations between those same behavioural factors and HIV infection.
Our study cohorts cannot be considered representative of young women in the two cities. Our behavioural eligibility criteria selected for a group of women with higher than average risk behaviours. The Rustenburg site offered the opportunity to demonstrate the impact of these selection factors: a representative household survey had been done there in 2008, 1 year before our study commenced. Our study cohort was younger, better educated, less likely to be employed and less likely to be married or live with a steady partner than all Rustenburg community residents. Most critically, only 3.4% of women in the household survey reported multiple sexual partners in the past 3 months compared with over 10% of women screened in our study who reported multiple partners in the past 1 month. So we make no claims for representativeness: our project deliberately set out to identify and follow a cohort with higher than average risk behaviours, in order to demonstrate the suitability of the sites for future prevention research.
Countervailing study strengths include the longitudinal design with high retention rates. Classification of the HIV outcome was highly accurate, using multiple monthly rapid tests confirmed by later PCR testing. Testing of stored baseline specimens allowed us to pinpoint seroconversion and rule out acute prestudy infections. Finally, direct prospective measurement of HIV infection circumvented the lingering issues with the accuracy of cross-sectional incidence estimation.
The high HIV prevalences and incidence rates in these cohorts in two smaller South African cities should spur vigorous HIV prevention efforts. The need for HIV care and treatment in these areas is clear, and while care is available, Free State Province experienced stock-outs of HIV antiretroviral drugs during the study.19
Our results also highlight the success of the collaborative capacity-building SIDI projects: these sites are highly suitable and ready for HIV prevention research and programming. Both sites added staff and were provided broad research training, and these new skills were immediately applied in a rigorous clinical research study. Dealing with local ethics committees and community stakeholders, recruiting and enrolling potentially higher risk women, administering informed consent, bringing participants back for regular study visits, giving ongoing risk reduction and HIV counselling and making referrals for continued healthcare, all within the context of Good Clinical Practice, mimicked future prevention trials. At the conclusion of its study, JOSHA in Bloemfontein was selected to implement an oral HIV prophylaxis trial. The Aurum Institute in Rustenburg is currently conducting a trial of a vaginal microbicide, along with other behavioural HIV studies. The national research capacity has been boosted and diffused to new sites outside the larger cities, which can only be a boon for future HIV and other clinical research in South Africa.