Using factor analyses to estimate the number of female sex workers across Malawi from multiple regional sources

Leveraging Routinely Collected Program Data to Inform Extrapolated Size Estimates for Key Populations in Namibia: Small Area Estimation Study

BACKGROUND

Estimating the size of key populations, including female sex workers (FSW) and men who have sex with men (MSM), can inform planning and resource allocation for HIV programs at local and national levels. In geographic areas where direct population size estimates (PSEs) for key populations have not been collected, small area estimation (SAE) can help fill in gaps using supplemental data sources known as auxiliary data. However, routinely collected program data have not historically been used as auxiliary data to generate subnational estimates for key populations, including in Namibia.

OBJECTIVE

To systematically generate regional size estimates for FSW and MSM in Namibia, we used a consensus-informed estimation approach with local stakeholders that included the integration of routinely collected HIV program data provided by key populations' HIV service providers.

METHODS

We used quarterly program data reported by key population implementing partners, including counts of the number of individuals accessing HIV services over time, to weight existing PSEs collected through bio-behavioral surveys using a Bayesian triangulation approach. SAEs were generated through simple imputation, stratified imputation, and multivariable Poisson regression models. We selected final estimates using an iterative qualitative ranking process with local key population implementing partners.

RESULTS

Extrapolated national estimates for FSW ranged from 4777 to 13,148 across Namibia, comprising 1.5% to 3.6% of female individuals aged between 15 and 49 years. For MSM, estimates ranged from 4611 to 10,171, comprising 0.7% to 1.5% of male individuals aged between 15 and 49 years. After the inclusion of program data as priors, the estimated proportion of FSW derived from simple imputation increased from 1.9% to 2.8%, and the proportion of MSM decreased from 1.5% to 0.75%. When stratified imputation was implemented using HIV prevalence to inform strata, the inclusion of program data increased the proportion of FSW from 2.6% to 4.0% in regions with high prevalence and decreased the proportion from 1.4% to 1.2% in regions with low prevalence. When population density was used to inform strata, the inclusion of program data also increased the proportion of FSW in high-density regions (from 1.1% to 3.4%) and decreased the proportion of MSM in all regions.

CONCLUSIONS

Using SAE approaches, we combined epidemiologic and program data to generate subnational size estimates for key populations in Namibia. Overall, estimates were highly sensitive to the inclusion of program data. Program data represent a supplemental source of information that can be used to align PSEs with real-world HIV programs, particularly in regions where population-based data collection methods are challenging to implement. Future work is needed to determine how best to include and validate program data in target settings and in key population size estimation studies, ultimately bridging research with practice to support a more comprehensive HIV response.

Differentiating the incidence and burden of HIV by age among women who sell sex: a systematic review and meta-analysis

INTRODUCTION

Young women who sell sex (YWSS) are at heightened risk of HIV acquisition and transmission and are among the least engaged in HIV services. There is insufficient epidemiologic evidence characterizing the burden of HIV among YWSS, particularly as compared to older WSS. These data are needed to design and tailor effective HIV prevention and treatment programmes for this population.

METHODS

We conducted two parallel systematic reviews and meta-analyses to define both the immediate and long-term HIV risks for YWSS, including among women engaged in sex work, survival sex and transactional sex. In the first review, we identified and synthesized published studies of HIV incidence comparing estimates for cisgender women ≤24 years of age versus >24. In the second review, we identified and synthesized studies of HIV prevalence, comparing estimates for cisgender women who initiated selling sex <18 versus ≥18 years. In both reviews, we completed a search of four databases for articles in any language and any geographic area published from 1 January 1980 until 12 February 2021. Included articles were assessed for quality and a random effects model was used to calculate pooled effect estimates for each review.

RESULTS AND DISCUSSION

We identified 12 studies for the HIV incidence review and 18 studies for the HIV prevalence review. In a meta-analysis, HIV incidence was elevated in younger (5.3 per 100 person-years [PY]; 95% confidence interval [CI]: 3.5, 7.1) compared to older women (2.8 per 100 PY; 95% CI: 1.7, 3.9), although CIs overlapped. HIV prevalence among those who initiated selling sex <18 years of age (28.8; 95% CI: 18.9, 38.7) was higher than those who initiated later (20.5; 95% CI: 12.4, 28.6).

CONCLUSIONS

These companion reviews offer an important perspective on the relative HIV risk of engaging in selling sex at a younger age. Our findings highlight the unique and intersectional challenges YWSS face, and the importance of ensuring that health services are tailored to meet their specific needs. Research and programming should routinely stratify data into meaningful age bands to differentiate and intervene within this population.