Mathematical Model Impact Analysis of a Real-Life Pre-exposure Prophylaxis and Treatment-As-Prevention Study Among Female Sex Workers in Cotonou, Benin

Lily Geidelberg, Kate M Mitchell, Michel Alary, Aminata Mboup, Luc Béhanzin, Fernand Guédou, Nassirou Geraldo, Ella Goma-Matsétsé, Katia Giguère, Marlène Aza-Gnandji, Léon Kessou, Mamadou Diallo, René K Kêkê, Moussa Bachabi, Kania Dramane, Christian Lafrance, Dissou Affolabi, Souleymane Diabaté, Marie-Pierre Gagnon, Djimon M Zannou, Flore Gangbo, Romain Silhol, Fiona Cianci, Peter Vickerman, Marie-Claude Boily, Lily Geidelberg, Kate M Mitchell, Michel Alary, Aminata Mboup, Luc Béhanzin, Fernand Guédou, Nassirou Geraldo, Ella Goma-Matsétsé, Katia Giguère, Marlène Aza-Gnandji, Léon Kessou, Mamadou Diallo, René K Kêkê, Moussa Bachabi, Kania Dramane, Christian Lafrance, Dissou Affolabi, Souleymane Diabaté, Marie-Pierre Gagnon, Djimon M Zannou, Flore Gangbo, Romain Silhol, Fiona Cianci, Peter Vickerman, Marie-Claude Boily

Abstract

Background: Daily pre-exposure prophylaxis (PrEP) and treatment-as-prevention (TasP) reduce HIV acquisition and transmission risk, respectively. A demonstration study (2015-2017) assessed TasP and PrEP feasibility among female sex workers (FSW) in Cotonou, Benin.

Setting: Cotonou, Benin.

Methods: We developed a compartmental HIV transmission model featuring PrEP and antiretroviral therapy (ART) among the high-risk (FSW and clients) and low-risk populations, calibrated to historical epidemiological and demonstration study data, reflecting observed lower PrEP uptake, adherence and retention compared with TasP. We estimated the population-level impact of the 2-year study and several 20-year intervention scenarios, varying coverage and adherence independently and together. We report the percentage [median, 2.5th-97.5th percentile uncertainty interval (95% UI)] of HIV infections prevented comparing the intervention and counterfactual (2017 coverages: 0% PrEP and 49% ART) scenarios.

Results: The 2-year study (2017 coverages: 9% PrEP and 83% ART) prevented an estimated 8% (95% UI 6-12) and 6% (3-10) infections among FSW over 2 and 20 years, respectively, compared with 7% (3-11) and 5% (2-9) overall. The PrEP and TasP arms prevented 0.4% (0.2-0.8) and 4.6% (2.2-8.7) infections overall over 20 years, respectively. Twenty-year PrEP and TasP scale-ups (2035 coverages: 47% PrEP and 88% ART) prevented 21% (17-26) and 17% (10-27) infections among FSW, respectively, and 5% (3-10) and 17% (10-27) overall. Compared with TasP scale-up alone, PrEP and TasP combined scale-up prevented 1.9× and 1.2× more infections among FSW and overall, respectively.

Conclusions: The demonstration study impact was modest, and mostly from TasP. Increasing PrEP adherence and coverage improves impact substantially among FSW, but little overall. We recommend TasP in prevention packages.

Trial registration: ClinicalTrials.gov NCT02237027.

Conflict of interest statement

The authors have no conflicts of interest to disclose.

Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc.

Figures

FIGURE 1.
FIGURE 1.
Model calibration: The results show model predictions from the 111 posterior parameter sets, in gray, green, and orange solid lines (median) and shaded regions (95% UI across all fits) representing prestudy, counterfactual (no PrEP or TasP), and 2-year PrEP/TasP study scenarios, respectively, compared with available fitting HIV prevalence and ART and PrEP coverage data shown in thick bars before 2015 (gray) and during the 2-year PrEP/TasP intervention study between 2015 and 2017 (orange). Results are shown for HIV prevalence (%) among (A) all women, (B) all men, (C) pFSW, (D) clients of FSW; ART coverage (%) among (E) HIV+ pFSW and (F) all HIV+; (G) number of pFSW on PrEP, and (H) on ART. Additional cross-validation data not used at the fitting stage are also presented in thin bars. Sections 6 and 7, Supplemental Digital Content 1, http://links.lww.com/QAI/B549 summarize additional fitting and cross-validation results, respectively.
FIGURE 2.
FIGURE 2.
Impact of the 2-year PrEP/TasP study for PrEP and TasP combined (scenario A1), PrEP alone (Sc A2), or TasP alone (Sc A3), among pFSW (“FSW”), clients, and the whole population (“All”) in terms of percentage of HIV infections prevented over (A) 2 years and (B) 20 years, and C) life-years gained (LYG) over 20 years, compared with counterfactual scenario (no PrEP; ART coverage 49% and 52% in 2017 and 2035, respectively). Box plots represent the median impact (central horizontal line), 25th to 75th percentiles (box), and 95% UI (whiskers) across 111 parameter sets. Labels in panels A and B show the median percentage (and number in brackets) of infections prevented; panel C shows median LYG. The PrEP and ART coverage represent median posterior values across all model fits for each scenario as shown in Table 3. *The median coverage of HIV- and HIV+ for PrEP and ART, respectively, at the end of the 2-year study. †Median coverage in 2035, 20 years after the start of PrEP/TasP study.
FIGURE 3.
FIGURE 3.
Impact of long-term 20-year PrEP (A, C) or TasP (B, D) intervention scenarios separately in terms of the percentage of infections prevented (A, B) and life-years gained (C, D) among pFSW (“FSW”) and the whole population (“All”), compared with the counterfactual scenario (no PrEP; 52% HIV+ pFSW ART coverage in 2035). Box plots represent the median impact (central horizontal line), 25th to 75th percentiles (box), and 95% UI (whiskers) across 111 parameter sets. The PrEP and ART coverages represent median posterior values in 2035 (among HIV- and HIV+ pFSW, respectively) across all model fits for each scenario as shown in Table 3. Adherence to PrEP assumed either as observed in the 2-year study (green), or perfect (orange). Labels in panels A and B show median percentage (and number in brackets) of infections prevented; panels C and D show median life-years gained.
FIGURE 4.
FIGURE 4.
Impact of combined 20-year PrEP interventions and TasP scale-ups (88% coverage HIV+ pFSW in 2035), in terms of the percentage of infections prevented (A) and life-years gained (B) among pFSW (“FSW”) and the whole population (“All”), compared with the counterfactual scenario (no PrEP; 52% HIV+ pFSW ART coverage in 2035). Box plots represent the median impact (central horizontal line), 25th to 75th percentiles (box), and 95% UI (whiskers) across 111 parameter sets. PrEP coverages represent median posterior values in 2035 (among HIV- pFSW) across all model fits for each scenario as shown in Table 3; adherence assumed as observed in 2-year study. Labels in panel A show median percentage (and number in brackets) of infections prevented; panel B shows median life-years gained.

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