HIV incidence estimation among female sex workers in South Africa: a multiple methods analysis of cross-sectional survey data

A Statistical Model for Inference of Recent and Incident HIV Infection Using Surveillance Data on Individuals Newly Diagnosed With HIV Infection in Scotland

BACKGROUND

To inform global ambitions to end AIDS, evaluation of progress toward HIV incidence reduction requires robust methods to measure incidence. Although HIV diagnosis date in routine HIV/AIDS surveillance systems are often used as a surrogate marker for incidence, it can be misleading if acquisition of transmission occurred years before testing. Other information present in data such as antibody testing dates, avidity testing result, and CD4 counts can assist, but the degree of missing data is often prohibitive.

METHODS

We constructed a Bayesian statistical model to estimate the annual proportion of first ever HIV diagnoses in Scotland (period 2015-2019) that represent recent HIV infection (ie, occurring within the previous 3-4 months) and incident HIV infection (ie, infection within the previous 12 months), by synthesizing avidity testing results and surveillance data on the interval since last negative HIV test.

RESULTS

Over the 5-year analysis period, the model-estimated proportion of incident infection was 43.9% (95% CI: 40.9 to 47.0), and the proportion of recent HIV infection was 21.6% (95% CI: 19.1 to 24.1). Among the mode of HIV acquisition categories, the highest proportion of recent infection was estimated for people who inject drugs: 27.4% (95% CI: 20.4 to 34.4).

CONCLUSIONS

The Bayesian approach is appropriate for the high prevalence of missing data that can occur in routine surveillance data sets. The proposed model will aid countries in improving their understanding of the number of people who have recently acquired their infection, which is needed to progress toward the goal of HIV transmission elimination.

PrEP discontinuation, cycling, and risk: Understanding the dynamic nature of PrEP use among female sex workers in South Africa

PrEP cycling among women is thought to be safe when there are distinct "seasons of risk." However, cyclical PrEP use over short periods may be associated with increased risk of HIV acquisition. We aimed to characterize key social ecological factors contributing toward PrEP cycling among female sex workers (FSW) in the context of high HIV risk. Semi-structured, in-depth interviews were conducted with 36 FSW at risk for HIV acquisition and 12 key informant (KI) service providers in eThekwini (Durban), South Africa from January-October 2020. FSW identified key factors driving temporary discontinuation of PrEP including relocation, lack of information on or difficulty coping with side effects, and delays in accessing PrEP. In many cases, FSW were motivated to restart PrEP once barriers were overcome. In contrast, KIs emphasized the importance of individual adherence to PrEP and reliance on personal risk assessments when counselling FSW on cycling decisions. FSW and KI perspectives highlight a disconnect between providers' recommendations on the potential for cyclical use of PrEP during periods of minimal risk and actual drivers among FSW causing temporary PrEP discontinuation. Further interventions supporting safe PrEP cycling are needed to ensure decisions around cycling are deliberate and guided by changes in HIV risk rather than external factors.

The effect on HIV transmission and cost-effectiveness of programmes for female sex workers in East, Central, and Southern Africa: a modelling study

BACKGROUND

HIV prevalence and incidence has declined in East, Central, and Southern Africa (ECSA), but remains high among female sex workers (FSWs). Sex worker programmes have the potential to considerably increase access to HIV testing, prevention, and treatment. We aimed to quantify these improvements by modelling the potential effect of sex worker programmes at two different intensities on HIV incidence and key health outcomes, and assessed the programmes' potential cost-effectiveness in order to help inform HIV policy decisions.

METHODS

Using a model previously used to review policy decisions in ECSA, we assumed a low-intensity sex worker programme had run from 2010 until 2023; this resulted in care disadvantages among FSWs being reduced, and also increased testing, condom use, and willingness to take pre-exposure prophylaxis (PrEP). After 2023, three policy options were considered: discontinuation, continuation, and a scale-up of the programme to high-intensity, which would have a broader reach, and higher influences on condom use, antiretroviral therapy (ART) adherence, testing, and PrEP use. Outputs of the key outcomes (the percentage of FSWs who were diagnosed with HIV, on ART, and virally suppressed; the percentage of FSWs with zero condomless partners, and HIV incidence) were compared in 2030. The maximum cost for a sex worker programme to be cost-effective was calculated over a 50-year time period and in the context of 10 million adults. The cost-effectiveness analysis was conducted from a health-care perspective; costs and disability-adjusted life-years were both discounted to present US$ values at 3% per annum.

FINDINGS

Compared with continuing a low-intensity sex worker programme until 2030, discontinuation of the programme was calculated to result in a lower percentage of FSWs diagnosed (median 88·75% vs 91·37%; median difference compared to continuation of a low-intensity programme [90% range] 2·03 [-4·49 to 10·98]), a lower percentage of those diagnosed currently taking ART (86·35% vs 88·89%; 2·38 [-3·69 to 13·42]), and a lower percentage of FSWs on ART with viral suppression (87·49% vs 88·96%; 1·17 [-6·81 to 11·53]). Discontinuation of a low-intensity programme also resulted in an increase in HIV incidence among FSWs from 5·06 per 100 person-years (100 p-y; 90% range 0·52 to 22·21) to 4·05 per 100 p-y (0·21 to 21·15). Conversely, comparing a high-intensity sex worker programme until 2030 with discontinuation of the programme resulted in a higher percentage of FSWs diagnosed (median 95·81% vs 88·75; median difference compared to discontinuation [90% range] 6·36 [0·60 to 18·63]), on ART (93·93 vs 86.35%; median difference 7·13 [-0·65 to 26·48]), and with viral suppression (93·21% vs 87·49; median difference 7·13 [-0·65 to 26·48]). A high-intensity programme also resulted in HIV incidence in FSWs declining to 2·23 per 100 p-y (0·00 to 14·44), from 5·06 per 100 p-y (0·52 to 22·21) if the programme was discontinued. In the context of 10 million adults over a 50-year time period and a cost-effectiveness threshold of US$500 per disability-adjusted life-year averted, $34 million per year can be spent for a high-intensity programme to be cost-effective.

INTERPRETATION

A sex worker programme, even with low-level interventions, has a positive effect on key outputs for FSWs. A high-intensity programme has a considerably higher effect; HIV incidence among FSW and in the general population can be substantially reduced, and should be considered for implementation by policy makers.

FUNDING

Wellcome Trust.

HIV incidence among women engaging in sex work in sub-Saharan Africa: a systematic review and meta-analysis

BACKGROUND

Women who engage in sex work in sub-Saharan Africa have a high risk of acquiring HIV infection. HIV incidence has declined among all women in sub-Saharan Africa, but trends among women who engage in sex work are poorly characterised. We synthesised data on HIV incidence among women who engage in sex work in sub-Saharan Africa and compared these with the total female population to understand relative incidence and trends over time.

METHODS

We searched MEDLINE, Embase, Global Health, and Google Scholar from Jan 1, 1990, to Feb 28, 2024, and grey literature for studies that reported empirical estimates of HIV incidence among women who engage in sex work in any sub-Saharan Africa country. We calculated incidence rate ratios (IRRs) compared with total female population incidence estimates matched for age, district, and year, did a meta-analysis of IRRs, and used a continuous mixed-effects model to estimate changes in IRR over time.

FINDINGS

From 32 studies done between 1985 and 2020, 2194 new HIV infections were observed among women who engage in sex work over 51 490 person-years. Median HIV incidence was 4·3 per 100 person years (IQR 2·8-7·0 per 100 person-years). Incidence among women who engage in sex work was eight times higher than matched total population women (IRR 7·8 [95% CI 5·1-11·8]), with larger relative difference in western and central Africa (19·9 [9·6-41·0]) than in eastern and southern Africa (4·9 [3·4-7·1]). There was no evidence that IRRs changed over time (IRR per 5 years: 0·9 [0·7-1·2]).

INTERPRETATION

Across sub-Saharan Africa, HIV incidence among women who engage in sex work remains disproportionately high compared with the total female population. However, constant relative incidence over time indicates HIV incidence among women who engage in sex work has declined at a similar rate. Location-specific data for women who engage in sex work incidence are sparse, but improved surveillance and standardisation of incidence measurement approaches could fill these gaps. Sustained and enhanced HIV prevention for women who engage in sex work is crucial to address continuing inequalities and ensure declines in new HIV infections.

FUNDING

Bill & Melinda Gates Foundation, UK Research and Innovation, National Institutes of Health.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Investigating the effects of cytokine biomarkers on HIV incidence: a case study for individuals randomized to pre-exposure prophylaxis vs. control

Introduction

Understanding and identifying the immunological markers and clinical information linked with HIV acquisition is crucial for effectively implementing Pre-Exposure Prophylaxis (PrEP) to prevent HIV acquisition. Prior analysis on HIV incidence outcomes have predominantly employed proportional hazards (PH) models, adjusting solely for baseline covariates. Therefore, models that integrate cytokine biomarkers, particularly as time-varying covariates, are sorely needed.

Methods

We built a simple model using the Cox PH to investigate the impact of specific cytokine profiles in predicting the overall HIV incidence. Further, Kaplan-Meier curves were used to compare HIV incidence rates between the treatment and placebo groups while assessing the overall treatment effectiveness. Utilizing stepwise regression, we developed a series of Cox PH models to analyze 48 longitudinally measured cytokine profiles. We considered three kinds of effects in the cytokine profile measurements: average, difference, and time-dependent covariate. These effects were combined with baseline covariates to explore their influence on predictors of HIV incidence.

Results

Comparing the predictive performance of the Cox PH models developed using the AIC metric, model 4 (Cox PH model with time-dependent cytokine) outperformed the others. The results indicated that the cytokines, interleukin (IL-2, IL-3, IL-5, IL-10, IL-16, IL-12P70, and IL-17 alpha), stem cell factor (SCF), beta nerve growth factor (B-NGF), tumor necrosis factor alpha (TNF-A), interferon (IFN) alpha-2, serum stem cell growth factor (SCG)-beta, platelet-derived growth factor (PDGF)-BB, granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and cutaneous T-cell-attracting chemokine (CTACK) were significantly associated with HIV incidence. Baseline predictors significantly associated with HIV incidence when considering cytokine effects included: age of oldest sex partner, age at enrollment, salary, years with a stable partner, sex partner having any other sex partner, husband's income, other income source, age at debut, years lived in Durban, and sex in the last 30 days.

Discussion

Overall, the inclusion of cytokine effects enhanced the predictive performance of the models, and the PrEP group exhibited reduced HIV incidences compared to the placebo group.

ART coverage and viral suppression among female sex workers living with HIV in eThekwini, South Africa: Baseline findings from the Siyaphambili study

In South Africa >60% of female sex workers (FSW) are living with HIV, the majority of whom are not virally suppressed. Identifying multi-level determinants of viral suppression is central to developing implementation strategies to promote retention in HIV care and viral suppression among FSW with unmet treatment needs. Adult cisgender FSW living with HIV for ≥6 months, conducting sex work as their primary source of income, and residing in Durban (South Africa) were enrolled into the Siyaphambili Study, a sequential multiple assignment randomized trial. Baseline viral load and CD4 were assessed, and an interviewer-administered survey was conducted, capturing socio-demographic, reproductive and sexual history and behaviors, vulnerabilities, substance use, mental health, and stigma. We assessed baseline determinants of viral suppression (<50 copies/mL) using bivariate and multivariable robust poisson regression, considering associations across the individual, network, environmental and macrostructural levels. From June 2018 -March 2020, 1,644 women were screened, with 1,391 eligible FSW living with HIV enrolled. The analyses were conducted among the 1,373 participants with baseline data. Overall, 65% (889/1,373) of participants were reported to be on antiretroviral therapy and 38% (520/1,373) were virally suppressed. In the multivariable model, FSW who experienced a lack of housing in the prior six months were less likely to be virally suppressed (aPR: 0.72, 95%CI 0.56-0.91), while older FSW (aPR: 1.46 95%CI: 1.16-1.83 for 30-39 years old vs. 18-29 years old; aPR: 2.15 95%CI: 1.64-2.80 for 40+ years vs. 18-29 years old) and FSW reporting hormonal or long-acting contraception use were more likely to be virally suppressed (aPR: 1.19 95% CI: 1.00-1.43). We found vulnerability to be high among FSW living with HIV in South Africa and identified individual and structural determinants associated with viral suppression. Taken together these results suggest optimizing HIV treatment outcomes necessitates supporting younger sex workers and addressing housing instability. Trial registration: NCT03500172.

Estimating the mortality risk correcting for high loss to follow-up among female sex workers with HIV in Durban, South Africa, 2018-2021

PURPOSE

This study assesses risk factors of loss to follow-up (LTFU) and estimates mortality risk among female sex workers (FSW) with HIV in Durban, South Africa, in 2018-2021.

METHODS

We used data from the Siyaphambili trial, which evaluated strategies for improved viral suppression. FSW with HIV aged ≥ 18 years with viral load ≥ 50 copies/mL were followed up for 18 months. LTFU was defined as absence from study or intervention visits for 6 months. We traced LTFU participants by calling/in-person visit attempts to ascertain their vital status. We used Cox regression to determine risk factors of LTFU and inverse probability of tracing weights to correct mortality risk.

RESULTS

Of 777 participants, 10 (1.3%) had died and 578 (74.4%) were initially LTFU. Among those LTFU, 36.3% (210/578) were traced successfully, with 6 additional deaths ascertained. Recent physical and sexual violence, and non-viral suppression were associated with increased LTFU. The unweighted and weighted 18-month mortality risks were 2.4% (95% CI: 0.8%-3.9%) and 3.7% (95% CI: 1.8%-5.9%), respectively.

CONCLUSIONS

LTFU is common among FSW with HIV in South Africa with additional investigation of vital status demonstrating under-ascertained mortality. These data suggest the need for comprehensively addressing risks for mortality among FSW.

The influence of type of sexual partnership on male condom use: empirical evidence from the South African construction industry

There are indications that gender has an effect on individual risk factors and pathways to HIV diagnoses and treatment. Furthermore, there is growing recognition that to improve HIV-related health outcomes for men, it is important to understand their experiences and perspectives. Perhaps because of the physical nature of construction work, the South African construction industry is dominated by men. Given that employed men are a hard-to-reach community population group, the construction workplace offers an ideal environment for data collection and delivery of non-health-facility-based HIV prevention and treatment interventions. Furthermore, workers in the construction industry have been identified as being at a heightened risk of acquiring HIV and AIDS because of work-related travel, the ubiquity of transactional sex around worker hostels and having an increased likelihood of multiple and concurrent sex partnerships. As a consequence, this study examines the association between condom use and sexual partnerships among men working in the construction industry. A purposive cross-sectional survey was used to collect data from 450 workers across 18 construction sites in the Western Cape province of South Africa. The types of sexual partnership had three categories: regular sex partnerships, casual sex partnerships and sex worker partnerships. Frequency of condom use was determined to be highest with casual sex partners (51.2%), followed by sex workers (40.6%) and regular sex partners (25.6%). Hierarchical multiple linear regression analysis was used to examine the demographic, experiential, behavioural and cognitive predictors of condom use across the three categories of sexual partnership. The results indicate that an individual's perception of control over condom use, and the perceived threat posed by HIV and AIDS are significantly associated with consistent condom use, even after accounting for differences in partner type. Implications of the findings are discussed, and directions for future research on the association between sexual partnerships and condom use are offered.

HIV incidence among women engaging in sex work in sub-Saharan Africa: a systematic review and meta-analysis

Introduction

HIV incidence among women in sub-Saharan Africa (SSA) has declined steadily, but it is unknown whether new infections among women who engage in sex work (WESW) have declined at a similar rate. We synthesised estimates of HIV incidence among WESW in SSA and compared these to the wider female population to understand levels and trends in incidence over time.

Methods

We searched Medline, Embase, Global Health, Popline, Web of Science, and Google Scholar from January 1990 to October 2022, and grey literature for estimates of HIV incidence among WESW in SSA. We included studies reporting empirical estimates in any SSA country. We calculated incidence rate ratios (IRR) compared to age-district-year matched total female population incidence estimates. We conducted a meta-analysis of IRRs and used a continuous mixed-effects model to estimate changes in IRR over time.

Results

From 32 studies between 1985 and 2020, 2,194 new HIV infections were observed in WESW over 51,000 person-years (py). Median HIV incidence was 4.3/100py (IQR 2.8-7.0/100py), declining from a median of 5.96/100py between 1985 and 1995 to a median of 3.2/100py between 2010 and 2020. Incidence among WESW was nine times higher than in matched total population women (RR 8.6, 95%CI: 5.7-12.9), and greater in Western and Central Africa (RR 22.4, 95%CI: 11.3-44.3) than in Eastern and Southern Africa (RR 5.3, 95%CI: 3.7-7.6). Annual changes in log IRRs were minimal (-0.1% 95%CI: -6.9 to +6.8%).

Conclusions

Across SSA, HIV incidence among WESW remains disproportionately high compared to the total female population but showed similar rates of decline between 1990 and 2020. Improved surveillance and standardisation of approaches to obtain empirical estimates of sex worker incidence would enable a clearer understanding of whether we are on track to meet global targets for this population and better support data-driven HIV prevention programming.

Evidence of HIV incidence reduction in young women, but not in adolescent girls, in KwaZulu-Natal, South Africa

Objectives

We estimated changes in the HIV incidence from 2013-2018 in Eshowe/Mbongolwane, KwaZulu-Natal, South Africa where Médecins Sans Frontières is engaged in providing HIV testing and care since 2011.

Methods

Using data from two cross-sectional household-based surveys conducted in 2013 and 2018, with consenting participants aged 15-59 years, we applied the incidence estimation frameworks of Mahiane et al and Kassanjee et al.

Results

In total, 5599 (62.4% women) and 3276 (65.9% women) individuals were included in 2013 and 2018, respectively. We found a mean incidence in women aged 20-29 years of 2.71 cases per 100 person-years (95% confidence interval [CI]: 1.23;4.19) in 2013 and 0.4 cases per 100 person-years (95% CI: 0.0;1.5) in 2018. The incidence in men aged 20-29 years was 1.91 cases per 100 person-years (95% CI: 0.87; 2.93) in 2013 and 0.53 cases per 100 person-years (95% CI: 0.0; 1.4) in 2018. The incidence decline among women aged 15-19 was -0.34 cases per 100 person-years (95% CI: -1.31;0.64).

Conclusions

The lack of evidence of incidence decline among adolescent girls is noteworthy and disconcerting. Our findings suggest that large-scale surveys should seriously consider focusing their resources on the core group of women aged 15-19 years.

Temporal trends in, and risk factors for, HIV seroconversion among female sex workers accessing Zimbabwe's national sex worker programme, 2009-19: a retrospective cohort analysis of routinely collected HIV testing data

BACKGROUND

The frequency of new HIV infections among female sex workers in sub-Saharan Africa is poorly understood. We used routinely collected data that enable unique identification of repeat HIV testers to assess temporal trends in seroconversion and identify associated risk factors for female sex workers accessing Sisters with a Voice, Zimbabwe's national sex worker programme.

METHODS

We pooled HIV testing data gathered between Sept 15, 2009, and Dec 31, 2019, from 36 Sisters programme sites in Zimbabwe. We included female sex workers aged 16 years or older with an HIV-negative test and at least one subsequent programme test. We calculated HIV seroconversion rates (using the midpoint between the HIV-positive test and the last negative test as the seroconversion date) and estimated rate ratios to compare 2-year periods by using Poisson regression, with robust SEs to account for clustering by site and adjusting for age and testing frequency to assess temporal trends. We did sensitivity analyses to explore assumptions about seroconversion dates and the effects of variation in follow-up time on our conclusions.

FINDINGS

Our analysis included data for 6665 female sex workers, 441 (7%) of whom seroconverted. The overall seroconversion rate was 3·8 (95% CI 3·4-4·2) per 100 person-years at risk. Seroconversion rates fell with time since first negative HIV test. After adjustment, there was evidence of a decrease in seroconversion rates from 2009 to 2019 (p=0·0053). In adjusted analyses, being younger than 25 years, and having a sexually transmitted infection diagnosis at a previous visit, were significantly associated with increased seroconversion rates. Our findings were mostly robust to sensitivity analyses, but when 1 month before an HIV-positive test was used as the seroconversion date, seroconversion rates no longer fell with time.

INTERPRETATION

We identified high rates of seroconversion shortly after linkage to programme services, which emphasises the need to strengthen HIV prevention programmes from first contact with female sex workers in Zimbabwe. New infections among female sex workers remain challenging to measure, but longitudinal analysis of routine testing data can provide valuable insights into seroconversion rates and associated risk factors.

FUNDING

UN Population Fund, Deutsche Gesellschaft für Internationale Zusammenarbeit, the Bill & Melinda Gates Foundation, The Global Fund to Fight AIDS, Tuberculosis and Malaria, US President's Emergency Plan for AIDS Relief, US Agency for International Development, and the Elton John AIDS Foundation.

Knowledge, Attitudes, and Practices of Sex Workers of Three South African Towns towards Female Condom Use and Contraceptives

Female sex workers are a marginalized and highly vulnerable population who are at risk of HIV and other sexually transmitted diseases, harassment, and unplanned pregnancies. Various female condoms are available to mitigate the severity of the consequences of their work. However, little is known about the acceptability and usage of female condoms and contraceptives among sex workers in small South African towns. This descriptive cross-sectional study of conveniently selected sex workers explored the acceptability and usage of female condoms and contraceptives among sex workers in South Africa using validated questionnaires. The data were analyzed using STATA 14.1. The 95% confidence interval is used for precision, and a p-value ≤ 0.05 is considered significant. Out of 69 female-only participants, 49.3% were unemployed, 53.6% were cohabiting, and 30.4% were HIV positive. The median age of entry into sex work was 16 years old. Participants reported use of condoms in their last 3 sexual encounters (62.3%), preference of Implanon for contraception (52.2%), barriers to condom use (81.2%), condoms not being accepted by clients (63.8%), being difficult to insert (37.7%), and being unattractive (18.8%). Participants who reported barriers to condom use were 90% more likely to have adequate knowledge than those who did not (PR = 1.9; p-value < 0.0001). Knowledge of condom use was an important factor in determining knowledge of barriers to their use. Reasons for sex work, sex workers' perceptions, and clients' preferences negatively affect the rate of condom use. Sex worker empowerment, community education, and effective marketing of female condoms require strengthening.