Hepatitis C in people who inject drugs in the Stockholm needle exchange program : incidence, spontaneous clearance and change in risk behaviour

Abstract: The major transmission route for hepatitis C virus (HCV) is sharing of unsterile injection equipment (needle/syringes and paraphernalia). Needle exchange programs (NEP) reduce injection risk behaviour and HCV spread among people who inject drugs (PWID). WHO has set a goal to eliminate HCV by the year 2030. To achieve this, a better understanding of the HCV spread among PWID is needed. The aims of this thesis were to study the HCV prevalence, incidence, spontaneous clearance, level of liver fibrosis and change in injection risk behaviour in PWID in the NEP in Stockholm. In Study I (n=1386), we found a high 60% baseline prevalence of HCV infection in PWID and that participants became HCV infected at an early stage. Thus, 50% became anti-HCV positive within 2-5 years after start of injection drug use (IDU). Furthermore, the participants had a low awareness of their HCV status. This will have influence on injection risk behaviour and will increase the risk of HCV transmission. These findings indicate that prevention and harm reduction measures need to be implemented early on. In Study II, we investigated the HCV incidence among NEP participants (n=584). Overall, a high incidence rate corresponding to 22/100 person-years was noted. Factors associated with becoming HCV infected were female gender, homelessness and amphetamine use. Spontaneously clearance among those with previous exposure of HCV was significantly higher than in those who were HCV naive. High coverage of NEP, scale-up of HCV treatment and participation in effective treatment for substance use disorders, such as opioid substitution treatment (OST) need to be implemented to reduce the HCV transmission. In Study III, we investigated the level of HCV related liver fibrosis with liver stiffness measurement (LSM) among participants (n=203) and found that 15% had advanced fibrosis in need of early treatment and HCC surveillance. We found that an age ≥ 40 years and duration of IDU ≥ 15 years in combination with an APRI score > 1, identified most participants with advanced fibrosis. This indicates that diagnostic work-up to detect advanced fibrosis can be simplified. In Study IV, we noted an overall significant reduction in injection risk behaviour of most baseline risk factors over time among participants (n=2860) in the NEP. Female gender, homelessness and amphetamine use were baseline determinants that correlated to an increased risk of sharing needle/syringes and paraphernalia, whereas OST was a protective factor. To conclude, our studies have contributed to an increased knowledge about the prevalence and incidence of HCV infections in PWID, which highlights the need to enforce effective harm reduction interventions to prevent the spread of HCV. To eliminate HCV by the year 2030, as proposed by WHO, further implementation of NEP together with a scale-up of HCV treatment among PWID and easy access to treatment for all participants is needed.