Modelling the impact of scaling up of HCV case finding and treatment for people who inject drugs in England

Background:

People who inject drugs (PWID) are disproportionately affected by Hepatitis C (HCV). England aims to reach the World Health Organisation (WHO) goal of eliminating HCV as a public health threat by 2030, through decreasing HCV incidence among PWID to <2 per 100 person-years. We assessed whether existing strategies will achieve these elimination goals.

Methods:

A dynamic HCV transmission model among PWID was used to project the impact of existing HCV testing and treatment services in four England regions: Bristol and Severn; Nottingham; Greater Manchester; and Northeast and Cumbria. The model included the pathway from testing to treatment in prisons, drug treatment centres (DTC), and other settings. These pathways were parameterised using data on the cascade-of-care and yearly number of treatments for these testing settings, with yearly bio-behavioural surveys among PWID also being used to parameterize and calibrate the model in a Bayesian framework. The model projected whether each region will reach the HCV elimination targets if existing testing and treatment initiatives are continued, and if not, then what improvements are needed from 2024 to achieve the targets.

Results:

Available data across the four regions estimate that 2029, 2848, and 2607 treatments (1069 per year among an estimated 35900 PWID) were undertaken in prisons, DTC, and other settings respectively, over 2016-2022. The time from diagnosis to treatment decreased from >1 year to <3 months in prisons and other testing settings over 2016-2020, and to 3-6 months in DTC. The scale-up in treatment is projected to have decreased chronic prevalence across these regions by 46.8-68.7% (range of medians) and HCV incidence by 46.8-69.2% over 2015-2022. Assuming continuation of ongoing testing and treatment rates from 2024, incidence will decrease by 66.0-86.9% to 1.2-3.0 per 100 person-years by 2030. Credibility intervals around these projections suggest the WHO elimination targets will be reached with 57-81% probability in three regions, but only with 21% probability in Nottingham. To achieve the target in Nottingham, screening should be increased in DTC (80% screened each year) or prisons (75% screened in their prison stay), which increases the probability of reaching the elimination target to 80% or 60%, respectively.

Conclusion:

Our modelling suggests that existing HCV testing and treatment pathways among PWID in England are sufficient to reach the WHO elimination targets in many regions, but further scale-up of testing may be needed in some regions.