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# Potential Impact of Targeted HIV Pre-Exposure Prophylaxis Uptake Among Male Sex Workers

## Abstract

### Sensitivity analyses

Sensitivity analyses were conducted to examine the robustness of the primary analyses to uncertain model parameters that might impact the observed effect of PrEP implementation, including the difference in the probabilities of optimal adherence and persistence among cisgender male sex workers relative to all other cisgender MSM, where cisgender male sex workers were 25% less likely to be achieve optimal adherence in a given time-step and 25% more likely to discontinue PrEP use in a given time-step.

## Results

In the absence of PrEP implementation, the model predicted that HIV prevalence would increase from 4.3% (95% SI: 4.0–4.6%) in January 2015 to 8.3% (7.5–9.0%) in December 2024 in the full population. These increases in HIV prevalence were evident across all subgroups (Fig. 1), including male sex workers (from 6.4% to 22.8%), their clients (from 4.2% to 12.8%), and all other MSM (from 4.2% to 7.4%). The model predicted an average of 92 new HIV infections per year (95% SI: 52–146), corresponding to an annual incidence rate of 0.39 infections per 100 person-years (95% SI: 0.22–0.63). Although the majority of new infections occurred among other MSM (67; 95% SI: 37–108), annual incidence rates were highest among male sex workers (1.89; 95% SI: 0.72–3.47) and their clients (0.92; 95% SI: 0.26 to 1.84).

### Epidemiologic impact of pre-exposure prophylaxis implementation

Among all MSM, the total number of new HIV infections was reduced in both the standard and focused uptake scenarios (Fig. 2, Panel A). With 15% of eligible MSM using PrEP for ten years in a standard uptake scenario, the number of new HIV infections was reduced by 34.5% (95% SI: 21.5–46.6%), representing 317 infections averted (95% SI: 198–429) over the ten-year simulation period. With equivalent coverage in a focused expansion uptake scenario, the number of new HIV infections was reduced by 58.1% (95% SI: 50.2–65.1%) overall, representing 534 infections averted (95% SI: 462–599).

Among male sex workers, the total number of new HIV infections was reduced in both the standard and focused uptake scenarios (Fig. 2, Panel B), with substantial reductions observed in the focused uptake scenarios. With 15% of eligible MSM using PrEP for ten years in a standard uptake scenario, the number of new HIV infections was reduced by 28.5% (95% SI: 7.4–45.9%) among male sex workers, representing 42 infections averted (95% SI: 11–67). In a targeted uptake scenario with equivalent coverage, the number of new HIV infections was reduced by 94.4% (95% SI: 89.9–98.0%), representing 140 infections averted among male sex workers (95% SI: 133–145). Focused expansion also increased the number of averted HIV infections among their clients (Fig. 2, Panel C) and all other MSM (Fig. 2, Panel D).

Despite increases in the number of HIV infections averted with increasing numbers of individuals using PrEP, the efficiency of PrEP use at the population level decreased with increasing coverage (Fig. 3), from 110 person-years of PrEP use per HIV infection averted (95% SI: 78–168) with 15% of eligible MSM using PrEP for ten years to 131 person-years of PrEP use per HIV infection averted (95% SI: 108–166) with 25% of eligible MSM using PrEP for ten years in standard uptake scenarios. However, relative to these standard uptake scenarios, focused uptake improved the efficiency of PrEP. In a focused uptake scenario where 25% of eligible MSM used PrEP for ten years, the number of person-years of PrEP use to avert one infection decreased to 97 person-years per HIV infection averted (95% SI: 88–108).

### Economic impact of pre-exposure prophylaxis implementation

Relative to no PrEP implementation, a standard uptake scenario where 15% of eligible MSM used PrEP for ten years generated an additional $356.6 billion in prevention-related costs (95% SI:$353.9–$359.7), but saved$106.9 billion in treatment-related costs (95% SI: $66.7–$144.6) by averting 317 new infections (95% SI: 198–429), resulting in a cost of $143,111 (95% SI:$85,090–$249,552) per QALY gained. Based on ICERs, no level of PrEP coverage in the standard uptake scenarios was considered cost-effective based on a threshold of$100,000 per QALY gained (Fig. 4).

Cost-effectiveness improved in focused uptake scenarios. A focused uptake scenario where 15% of eligible MSM used PrEP for ten years generated $356.6 billion in prevention-related costs (95% SI:$353.7–$359.5), but saved$180.1 billion in treatment-related costs (95% SI: $155.7–$201.9) by averting 534 new infections (95% SI: 462–599), resulting in a cost of $57,180 per QALY gained (95% SI:$44,135–$74,064) relative to a scenario without PrEP implementation and a savings of$57,802 per QALY gained (95% SI: $55,451–$60,158) relative to a standard uptake scenario with equivalent coverage. Based on ICERs, focused uptake scenarios where 15% and 20% of eligible MSM used PrEP for ten years were considered cost-effective relative to a scenario without PrEP implementation (Fig. 4) and cost-saving relative to standard uptake scenarios with equivalent coverage.

### Sensitivity analyses

In a sensitivity analyses in which male sex workers were 25% less likely to be adherent and retained on PrEP than other MSM, the number of new HIV infections increased by 13.1% (95% SI: -10.5–52.7%) in the standard uptake scenario where 25% of eligible MSM used PrEP for ten years. Similar increases were observed in the focused uptake scenario with equivalent coverage (34.6%; 95% SI: 10.3–60.5%). The cost per QALY gained increased by 90.0% (95% SI: 35.0–187.2%) in the standard uptake scenario and by 38.0% (95% SI: 9.2–78.5%) in the focused uptake scenario, reducing its cost-effectiveness.

## Discussion

Few studies have focused on PrEP implementation among cisgender male sex workers in the United States and, to date, no published studies have assessed the potential epidemiologic and economic impacts of focused expansion of PrEP use in this population. Rhode Island is a unique context for the study of HIV prevention among cisgender male sex workers. Between 1980 and 2009, prostitution was legal as there was no specific statute to define the act and outlaw it, although associated activities, such as solicitation, brothel-keeping, and procuring were illegal25. In addition, the capital city of Providence is home to Project Weber/RENEW, the only organization in the country dedicated exclusively to addressing the needs of male sex workers15. As such, there is an existing infrastructure to provide health and social services for this population, making the ambitious intervention coverage goals identified possible.

Our results suggest that focused expansion of PrEP use among cisgender male sex workers may be effective in reducing the overall number of new HIV infections in this low incidence setting in a manner that is cost-effective. By increasing the proportion of individuals on PrEP who are cisgender male sex workers from 5% (in a standard uptake scenario) to 25% (in a focused uptake scenario) while maintaining an overall coverage of 15% for ten years, an additional 217 HIV infections are averted in the overall population. Previous studies have referred to sex workers as a “core group”– a small population with a high number of sexual contacts that often has disproportionate role in sustaining transmission26,27. By averting HIV infections among cisgender male sex workers, further transmission events to their clients and other cisgender MSM are prevented, producing larger reductions in HIV incidence relative to other strategies. Previous research has shown that ensuring access to those most at risk for HIV infection can increase the impact of PrEP expansion in low incidence settings even in the context of expanding treatment access28.

However, despite these potential benefits, there are challenges in reaching these high levels of intervention coverage among cisgender male sex workers, with a death of evidence about how to best deliver PrEP to male sex workers. Nonetheless, recent studies have shown rapidly increasing interest in PrEP use among male sex workers29,30, suggesting that developing service delivery models that meet the needs of male sex workers should a public health priority. In a recent qualitative analysis with cisgender male sex workers in Rhode Island, Underhill and colleagues (2018) found that cyclical changes in risk among male sex workers responded to fluctuations in addiction severity, giving rise to a so-called “access-interest paradox”3. Much of male sex work practiced in Rhode Island is street-based and many individuals engage in sex work to meet survival and substance use needs15. During periods of intense substance use, individuals reported increased engagement in sex work and commensurate increases in interest using PrEP, but due to scarce resources and other barriers, many individuals were unable to access PrEP during these periods3. During times of reduced drug use and less frequent engagement in transactional sex, individuals reported greater access to resources to support PrEP initiation, but lower interest due to perceived lower risk for HIV infection3. Further, the results of our sensitivity analyses suggest that the impact of focused expansion of PrEP use among cisgender male sex workers may be diminished by reduced adherence and persistence. Our results, in combination with the existing literature3,4,5,6, suggest that additional outreach and financial support may be needed to support PrEP initiation, adherence, and persistence during these periods, including support in enrolling in health insurance, in context of interventions that reduce social and structural vulnerability such as the decriminalization of sex work25.

These analyses are subject to some limitations. First, the model does not account for the possibility that PrEP use may facilitate the emergence of drug resistance among those who initiate PrEP during acute stage HIV infection or those who acquire HIV infection with sub-therapeutic drug concentrations, although a previous economic evaluation found that potential emergent drug resistance does not impact estimates of effectiveness or cost-effectiveness of PrEP use at the population level31. Second, given that PrEP use has additional benefits associated with regular screening for sexually transmitted infections (STIs)32, our estimates may underestimate the true epidemiologic and economic impacts of PrEP implementation by focusing our analyses on costs saved due to averted HIV infections. Third, our findings are limited by key assumptions. These findings assume a population of male sex workers with elevated HIV prevalence and less frequent use of existing prevention strategies than other MSM. The impacts of targeted PrEP uptake among male sex workers may vary in settings with lower HIV prevalence or different distributions of behavioral risk factors among male sex workers, or in other legal or socio-structural contexts. Furthermore, we assumed stable PrEP coverage (such that scenarios could be directly compared), as opposed to increasing coverage over time, which has been observed in many settings. We also assumed no change in sexual risk behavior following periods of PrEP discontinuation. Given the lack of empirical data to guide an assumption, future modeling studies should examine the impact of increased sexual risk behavior after PrEP discontinuation on HIV transmission. Fourth, the model was parameterized to represent cisgender men only. As such, these findings cannot be readily generalized to transgender MSM. Fifth, local data were used to parameterize the model where possible, but as in many individual-based models, some input parameters were derived from different source populations, which may introduce bias and impact both the representativeness of the model and the generalizability of the simulation outputs33.

Targeted expansion of PrEP use among male sex workers may be a cost-effective strategy for reducing HIV incidence in this vulnerable population, their clients, and all other MSM. Strategies that prioritize male sex workers for PrEP initiation are considered cost-saving relative to those that do not. As such, interventions that reduce barriers to PrEP initiation and persistence among male sex workers are urgently needed.

## Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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## Acknowledgements

This research is supported by funding from the National Institute on Drug Abuse (DP2DA040236 to BDLM and R21DA035113 to KBB and MJM) and the National Institute of Mental Health (R21MH109360 to BDLM and PAC and R34MH110369 to MJM, KBB, and PAC). In addition, Mr. Goedel is supported by funding from the National Institute of Mental Health (F31MH12112) and Dr. Safren is supported by funding from the National Institutes on Drug Abuse (K24DA040489). The authors wish to thank S. Bessey, MS, Maxwell S. Krieger, BS, and Jesse L. Yedinak, MPA for their research and administrative assistance. Portions of these data were presented in a poster format at the 10th International AIDS Society Conference on HIV Science in Mexico City, Mexico in July 2019.

## Author information

Authors

### Contributions

W.C.G. conceived the study with K.B.B. and B.D.L.M. providing input on the design the study. M.R.F.K. implemented the computational model. W.C.G. analyzed the model output, generated figures, and wrote a first draft of the manuscript with input from K.B.B. and B.D.L.M. M.J.M., S.A.S., K.H.M. and P.A.C. assisted in interpretation and presentation of the results and analysis. All authors revised or reviewed the manuscript critically and approved the final version. K.B.B. and B.D.L.M. take final responsibility for the accuracy of the results and overall fidelity of the manuscript.

### Corresponding author

Correspondence to Brandon D. L. Marshall.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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Goedel, W.C., Mimiaga, M.J., King, M.R.F. et al. Potential Impact of Targeted HIV Pre-Exposure Prophylaxis Uptake Among Male Sex Workers. Sci Rep 10, 5650 (2020). https://doi.org/10.1038/s41598-020-62694-5

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