Theme: Epidemiology & Public Health Research Year: 2022
In Scotland, there is an ongoing effort to deliver direct-acting anti-viral treatment (DAA) against the
Hepatitis C virus (HCV) to people who inject drugs (PWID). The administration of DAAs began in 2015
and has been gradually increasing to date, particularly in the region of Tayside. In this work, we
evaluate the impact of DAAs on HCV viraemia among PWID over time and by region and investigate
how this impact differs according to treatment intensity.
We evaluate the impact of DAAs (the intervention) using longitudinal data on HCV viraemia and
antibody prevalence among PWID during the period 2010-2020 from the Needle Exchange
Surveillance Initiative (NESI). We aggregate the data by region and fit a Bayesian binomial differencein-differences (DID) model to the proportion of HCV RNA positive (RNA+) individuals among those
who are HCV antibody-positive. The fitted model provides a counterfactual for HCV viremia in the
absence of intervention which, compared with the observed figures, yields an estimate of the
treatment’s impact. We define treatment intensity as the number of new DAA treatments divided by
the estimated number of PWID in the population and include as a covariate in the DID model.
For each Scottish region, we compare the estimated prevalence in 2020 to the pre-intervention
average; the posterior distributions of these quantities are shown in Figure 1. The estimated
reduction in Tayside, Greater Glasgow & Clyde and Rest of Scotland is 44.4%, 32.2% and 17.5%,
respectively. Initial results suggest that treatment intensity has a significant effect on the magnitude
of these effects.
Our analyses suggests that introduction of DAAs has led to a significant decrease in HCV viraemia
among people who inject drugs.
Disclosure of Interest: None