Modelling The Impact of The Care Cascade Amongst Young People Who Inject Drugs in San Francisco

Author: Hannah Fraser Shelley Facente Adelina Artenie Sheena Patel Erin Wilson Willi McFarland Kim Page Meghan Morris Peter Vickerman Peter

Theme: Epidemiology & Public Health Research Year: 2022

Young adult (18-30 years) people who inject drugs (YPWID) experience the highest hepatitis C virus
(HCV) prevalence, but treatment remains disproportionately low. We evaluated progress toward
achieving WHO HCV elimination goals by modelling the current HCV care cascade (CC) and how
changes in accessing testing and treatment affect HCV incidence among YPWID in San Francisco.
We developed a dynamic HCV transmission model among PWID, parameterized and calibrated to
various biobehavioural survey datasets from San Francisco, including 2018 estimates for the
coverage of opioid substitution therapy (51%), prevalence of unstable housing (74%) and antibodyprevalence among PWID (77%). The model included CC estimates for YPWID: 63% of infections RNAconfirmed, 72% aware of their status and 33% ever initiating treatment. Continuing this existing CC,
we modelled likely progress towards achieving elimination goals (≥80% reduction in incidence over
2015-2030) and interim progress by 2025. We also estimated the impact of removing current testing
and treatment from 2021.
Continuing the current CC, the model projects the elimination goals will be met among YPWID and
PWID over 2015-2030, with incidence among YPWID decreasing by 92.4% (95% credibility interval
[95%CrI]:83.4–95.8%). Over 2015-2025, the model projects an 81.4% (71.6–86.8%) reduction in HCV
incidence, from 15.6 per 100 person-years (/100pyrs) (10.9–21.3) in 2015 to 3.0/100pyrs (1.7-5.2) in
2025. Over this period, the model projects 1,848 (1,270–2,795) YPWID will have been diagnosed
with chronic infection and 1,059 (404–1,787) will have been treated. Removing current testing and
treatment from 2021 decreases the impact on incidence, reducing only by 58.0% (48.0–64.0%) over
2015-2025, to 6.6/100pyrs (4.2–10.9) in 2025, with incidence increasing to 7.1/100pyrs (95%CrI:4.4–
12.0) by 2030.
Results indicate that the elimination goals are achievable with the current care cascade, however
continued engagement with services is key to targets being met.
Disclosure of Interest Statement:

SNF has received consulting fees from Gilead Sciences outside the
conduct of the study; PV reports an unrestricted grant from Gilead Sciences, outside the conduct of
the study; MDM reports grants from Gilead Sciences, outside the conduct of the study; all other
authors have no conflicts of interest to disclose.

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