Globally, over 70 million people are infected with hepatitis C virus (HCV), leading to an estimated 400,000 deaths per year. Co-infection with HIV poses even greater risks due to accelerated rates of HCV related liver damage. Within men who have sex with men (MSM) HCV is more concentrated in those with HIV: in the UK 10% of MSM with HIV are co-infected, whereas HCV prevalence is 1% in HIV negative MSM. Yet reasons for this disparity are not fully clear. To tackle this global epidemic, in 2015 the World Health Organisation (WHO) and the UK National Health Service (NHS) announced their targets to eliminate HCV; by reducing HCV incidence by 90% by 2030 and 2025 respectively.
In this thesis we utilise a compartmental transmission model, parameterized with UK behavioural data and biological factors associated with HIV and HCV co-infection to explore the feasibility of these HCV elimination targets and determine the key factors which may influence their success. This analysis was
undertaken accounting for the changing landscape of (1) HCV treatment and prevention initiatives, such as the scale up of direct acting antivirals (DAAs) and (2) the evolution of HIV prevention through the introduction of pre-exposure prophylaxis (PrEP). PrEP use offers individuals an 86% reduced risk of HIV acquisition, but with PrEP’s growing uptake, data is increasingly pointing to the rise of risk compensatory behaviours, including reducing condom usage or changes in sexual mixing.
Our results indicate behavioural and not biological factors are largely accountable for the pattern of HCV infection; specifically preferential mixing by HIV status and heterogeneity in the number of sexual partners between MSM. We projected that HCV elimination in UK MSM is possible by both 2030 and 2025, requiring enhanced HCV screening in all MSM and faster initiation of treatment than in the pre-DAA era. Furthermore, by incorporating this extra screening into routine sexual health appointments, our proposed elimination strategies, for both the 2025 and 2030 targets, are also cost-effective at the willingness to pay threshold of <£20,000 per quality adjusted life-year (QALY) set by the NHS.
In conclusion, HCV elimination within UK MSM is possible whilst being cost-effective, but requires a scale up of HCV screening over all MSM, not just those with HIV co-infection. It is also important to mitigate risk compensatory behaviours associated with PrEP use, as our projections have shown these behaviours to be both drivers of the UK HCV epidemic pattern in MSM, as well as highly influential to the overall cost-effectiveness of implementing our HCV elimination strategies.
|Date of Award
|1 Oct 2019
- The University of Bristol
|A J Ganesh (Supervisor) & Peter T Vickerman (Supervisor)