Optimal targeting of Hepatitis C virus treatment among injecting drug users to those not enrolled in methadone maintenance programs

Abstract

Background: This work used mathematical modelling to explore effective policy for hepatitis C virus (HCV) treatment in Australia in the context of methadone maintenance treatment (MMT).Method: We consider two models to depict HCV in the population of injecting drug users (IDU) within Australia. The first model considers the IDU population as a whole. The second model includes separate components for those that are or are not enrolled in MMT. The impact of different levels of HCV treatment and its allocation dependent on MMT status were then determined in terms of the steady state levels of each of these models.Results: Although increasing levels of HCV treatment decrease chronic infection prevalence, initially numbers of acutely infected can rise. This is caused by the high rate of reinfection. We find that no matter the extent of HCV treatment, HCV prevalence cannot be eliminated without limiting risk behaviour. Assuming equal adherence to HCV therapy between MMT and non-MMT, over 84% of HCV treatment should be allocated to those not in MMT. Only if adherence to HCV therapy in non MMT patients falls below 44% of that in MMT then treatment should be preferentially directed to those in MMT.Conclusions: Contrary to generally held beliefs regarding HCV treatment the majority of therapy should be allocated to those that are still actively injecting. This is due to rates of reinfection and to the high turnover of individuals in MMT. Higher adherence to HCV therapy in MMT would need to be achieved before this changed.

Can antiviral therapy for hepatitis C reduce the prevalence of HCV among injecting drug user populations? A modeling analysis of its prevention utility

“…Only one other modeling study has considered the impact of HCV treatment on prevalence [33]. Although a similar model structure was used, our analysis produced more optimistic projections because our fixed number treatment term is a more realistic model of antiviral treatment capacity and delivery, in contrast to a treatment term which diminishes as the prevalence decreases.…”

Model for hepatitis C virus transmissions

“…The rate of recovery from acute infection σ is estimated at 0.5 per year and the rate of progression to chronic infection ε at 1.5 per year, which is equivalent to a mean duration of acute infection of 6 months and an overall rate of clearance of 25% [51]. The rate of recovery from chronic infection δ is estimated at 0.002 per year [8].…”

“…A susceptible-infected-removed (SIR) model is used by Kretzschmar and Wiessing [32] to study the transmission of HCV among injecting drug users (IDUs). Models that allow for waning immunity of the susceptible-infected-removed-susceptible (SIRS) type are used by Das et al [17] and Zeiler et al [51].…”

Global analysis of a mathematical model for Hepatitis C virus transmissions

“…Unsafe therapeutic injections and transfusions are the major modes of transmission in the developing countries, especially in countries where age-specific seroprevalence rates suggest ongoing increased risk of HCV infection (Wasley and Alter, 2000). In developed countries with high seroprevalence in older age groups, unsafe therapeutic injections probably had a substantial role in HCV transmission 30-50 years ago, and may persist as an important cause of transmission in isolated, hyperendemic areas (Zeiler et al, 2010;Guadagnino et al, 1997;Okayama et al, 2002).…”