Abstract and Introduction
Little is known about the level of testing required to sustain elimination of hepatitis C (HCV), once achieved. In this study, we model the testing coverage required to maintain HCV elimination in an injecting network of people who inject drugs (PWID). We test the hypothesis that network-based strategies are a superior approach to deliver testing. We created a dynamic injecting network structure connecting 689 PWID based on empirical data. The primary outcome was the testing coverage required per month to maintain prevalence at the elimination threshold over 5 years. We compared four testing strategies. Without any testing or treatment provision, the prevalence of HCV increased from the elimination threshold (11.68%) to a mean of 25.4% (SD 2.96%) over the 5-year period. To maintain elimination with random testing, on average, 4.96% (SD 0.83%) of the injecting network needs to be tested per month. However, with a 'bring your friends' strategy, this was reduced to 3.79% (SD 0.64%) of the network (p < .001). The addition of contact tracing improved the efficiency of both strategies. In conclusion, we report that network-based approaches to testing such as 'bring a friend' initiatives and contact tracing lower the level of testing coverage required to maintain elimination.
The World Health Organization (WHO) has set a target of the year 2030 for the global elimination of hepatitis C virus (HCV), defined by three parameters: (1) identification of 90% of prevalent cases, (2) successful treatment of 80% of identified cases and (3) 80% reduction in incident infections. In the absence of measuring trends in HCV incidence in real-time, a fall in HCV prevalence is a valid way to measure progress towards elimination. Widespread provision of HCV testing services is critical to achieve elimination; in some areas, this is being achieved and HCV elimination targets are likely to be met,[4–6] while others are not on track, and the COVID-19 pandemic has further reduced the likelihood of success.
Targeted testing services towards those at higher risk of infection will be needed to maintain elimination, once achieved. Accordingly, where initial elimination targets are met, provision of targeted testing for populations most at risk of re-introduction of infection must continue. It is essential that sustainable testing services are developed, implemented effectively and receive long-term funding.
The individuals who will remain most at risk of incident HCV infection are people who inject drugs (PWIDs) via the sharing of injecting paraphernalia. Therefore, targeted testing services must be effective in reaching this population. The development of accessible testing services for these individuals has been critical for successful micro-elimination programmes. However, the level of testing activity required to maintain elimination and prevent HCV becoming re-established in injecting networks has not been quantified. Without an understanding of how much testing will be required, it will be difficult to allocate appropriate resources towards maintaining elimination within the population.
A long-term targeted testing strategy for HCV in PWID must also be efficient and effective. The value of social network-based recruitment is that it can increase engagement of otherwise 'hidden' PWID. Such an approach has two main implications—firstly, it would mean testing is focused on PWID with multiple injecting partners; PWID with greater network connectivity are more likely to be a social contact of another PWID. Secondly, it would facilitate a contact tracing (CT) testing strategy within the social network of HCV-positive PWID. This is evidenced by peer referral testing for HCV in PWID in a real-world setting, and its effectiveness in achieving the elimination objectives, relative to random testing, has been shown in a recent modelling study. The utility of CT in PWID with HCV has been the subject of a recent review, but to date there is no simulated or real-world evidence testing its potential effectiveness.
The present study will address three questions in an injecting network of 689 PWID based on real-world empirical data. Firstly, what happens after elimination is achieved if testing for HCV stops? Secondly, what testing activity is required to maintain HCV prevalence at or below the elimination threshold? Thirdly, which treatment strategy is most effective? The answers will have real-world implications for HCV care after elimination targets are met.
J Viral Hepat. 2023;30(3):242-249. © 2023 Blackwell Publishing