Modelling the impact of a national scale-up of interventions on hepatitis C virus transmission among people who inject drugs in Scotland

Hannah Fraser, Christinah Mukandavire, Natasha K. Martin, David Goldberg, Norah Palmateer, Alison Munro, Avril Taylor, Matthew Hickman, Sharon Hutchinson, Peter Vickerman

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Abstract

Background and Aims: To reduce hepatitis C virus (HCV) transmission among people who inject drugs (PWID), Scottish Government-funded national strategies, launched in 2008, promoted scaling-up opioid substitution therapy (OST) and needle and syringe provision (NSP), with some increases in HCV treatment. We test whether observed decreases in HCV incidence post-2008 can be attributed to this intervention scale-up. Design: A dynamic HCV transmission model among PWID incorporating intervention scale-up and observed decreases in behavioural risk, calibrated to Scottish HCV prevalence and incidence data for 2008/09. Setting: Scotland, UK. Participants: PWID. Measurements: Model projections from 2008 to 2015 were compared with data to test whether they were consistent with observed decreases in HCV incidence among PWID while incorporating the observed intervention scale-up, and to determine the impact of scaling-up interventions on incidence. Findings: Without fitting to epidemiological data post-2008/09, the model incorporating observed intervention scale-up agreed with observed decreases in HCV incidence among PWID between 2008 and 2015, suggesting that HCV incidence decreased by 61.3% [95% credibility interval (CrI) = 45.1-75.3%] from 14.2/100 person-years (py) (9.0-20.7) to 5.5/100 py (2.9-9.2). On average, each model fit lay within 84% (10.1/12) of the confidence bounds for the 12 incidence data points against which the model was compared. We estimate that scale-up of interventions (OST + NSP + HCV treatment) and decreases in high-risk behaviour from 2008 to 2015 resulted in a 33.9% (23.8-44.6%) decrease in incidence, with the remainder [27.4% (17.6-37.0%)] explained by historical changes in OST + NSP coverage and risk pre-2008. Projections suggest that scaling-up of all interventions post-2008 averted 1492 (657-2646) infections over 7 years, with 1016 (308-1996), 404 (150-836) and 72 (27-137) due to scale-up of OST + NSP, decreases in high-risk behaviour and HCV treatment, respectively. Conclusions: Most of the decline in hepatitis C virus (HCV) incidence in Scotland between 2008 and 2015 appears to be attributable to intervention scale-up (opioid substitution therapy and needle and syringe provision) due to government strategies on HCV and drugs.

Original languageEnglish
Pages (from-to)2118-2131
Number of pages14
JournalAddiction
Volume113
Issue number11
Early online date10 Jul 2018
DOIs
Publication statusPublished - 7 Oct 2018

Keywords

  • Hepatitis C
  • Injecting drug users
  • Needle and syringe programmes
  • Opioid substitution therapy
  • People who inject drugs
  • Scotland

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    Fraser, H., Mukandavire, C., Martin, N. K., Goldberg, D., Palmateer, N., Munro, A., Taylor, A., Hickman, M., Hutchinson, S., & Vickerman, P. (2018). Modelling the impact of a national scale-up of interventions on hepatitis C virus transmission among people who inject drugs in Scotland. Addiction, 113(11), 2118-2131. https://doi.org/10.1111/add.14267