Modelling the effect of market forces on the impact of introducing human immunodeficiency virus pre‐exposure prophylaxis among female sex workers

Abstract

Pre-exposure prophylaxis (PrEP) to prevent human immunodeficiency virus (HIV) enables female sex workers (FSWs) to protect themselves from HIV without relying on clients using condoms. Yet, because PrEP reduces HIV risk, financial incentives to not use condoms may lead to risk compensation: reductions in condom use and/or increases in commercial sex, and may reduce the price of unprotected sex. In this analysis, we integrate market forces into a dynamic HIV transmission model to assess how risk compensation could change the impact of PrEP among FSWs and clients. We parameterise how sexual behavior may change with PrEP use among FSWs using stated preference data combined with economic theory. Our projections suggest the impact of PrEP is sensitive to risk compensatory behaviors driven by changes in the economics of sex work. Condom substitution could reduce the impact of PrEP on HIV incidence by 55%, while increases in the frequency of commercial sex to counter decreases in the price charged for unprotected sex among PrEP users could entirely mitigate the impact of PrEP. Accounting for competition between PrEP users and nonusers exacerbates this further. Alternative scenarios where increases in unprotected sex among PrEP users are balanced by decreases in non-PrEP users have the opposite effect, resulting in PrEP having much greater impact. Intervention studies need to determine how HIV prevention products may change the economics of sex work and provision of unprotected sex to enable a better understanding of their impact. K E Y W O R D S economics of sex work, HIV prevention, pre-exposure prophylaxis, South Africa, transmission model This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Impact and cost‐effectiveness of the national scale‐up of HIV pre‐exposure prophylaxis among female sex workers in South Africa: a modelling analysis

“…Studies have previously modelled the impact and costeffectiveness of PrEP in different sub-Saharan African settings and populations [8], including FSWs, with some of these considering SA [31,[41][42][43][44][45][46][47][48][49]. These studies suggest that PrEP use among FSWs can reduce transmission among FSWs, but that the overall population-level impact may be small in generalized epidemics where FSWs may contribute less to HIV transmission [10].…”

Understanding the contexts in which female sex workers sell sex in Kampala, Uganda: a qualitative study

“…Globally women who sell sex face a disproportionately large risk of HIV acquisition compared to the general population [1][2][3]. Among those at greatest risk are female sex workers (FSWs) in low-and middle-income countries (LMICs) who are 13.5 times more likely to acquire HIV relative to the general population [3,4].…”