Towards elimination of hepatitis C in Oslo: Cross-sectional prevalence studies among people who inject drugs.

BACKGROUND: Norway aims to eliminate hepatitis C virus (HCV) infection within the end of 2023. Before the introduction of direct-acting antivirals, the prevalence of chronic HCV infection among people who inject drugs (PWID) in Oslo was 40-45 %. The primary aim of the study was to assess changes in HCV prevalence among PWID in Oslo from 2018 to 2021. The secondary aim was to assess change in prevalence in selected subgroups. METHODS: Point prevalence studies were conducted in 2018 and 2021 among PWID attending low-threshold health services in downtown Oslo. Assessments included blood samples analysed for anti-HCV and HCV RNA, and a questionnaire about drug use. Information about previous HCV treatment was only collected in the 2021 cohort. We calculated HCV RNA prevalence estimates for 2018 and 2021 and used logistic regression analysis to identify factors associated with detectable HCV RNA and previous HCV treatment. RESULTS: A total of 281 and 261 participants were included in 2018 and 2021, respectively. The median age was 40.6 and 44.0 years, 73.7 % and 72.8 % were men, and 74.5 % and 78.6 % reported recent (past four weeks) injecting drug use, respectively. HCV RNA prevalence decreased significantly from 26.3 % (95 % CI 21.3-31.9) in 2018 (74 of 281) to 14.2 % (95 % CI 10.2-19.0) in 2021 (37 of 261). The odds of detectable HCV RNA were significantly lower in 2021 compared to 2018 (aOR 0.41; 95 % CI 0.26-0.67). In the 2021 cohort, detectable HCV RNA was associated with recent amphetamine injecting (aOR 7.21; 95 % CI 1.41-36.95), and mixed heroin/amphetamine injecting (aOR 7.97; 95 % CI 1.55-41.07). The odds of previous treatment were lower among women (aOR 0.52; 95 % CI 0.27-1.00). CONCLUSION: A substantial decrease in HCV RNA prevalence among PWID in Oslo between 2018 and 2021 was observed. To reach elimination, adaptive services must be further developed.

Hepatitis C treatment and reinfection surveillance among people who inject drugs in a low-threshold program in Oslo, Norway.

BACKGROUND: The aims were to evaluate HCV treatment effectiveness, estimate reinfection rates, and demonstrate the feasibility of reinfection surveillance and retreatment among marginalized people who inject drugs (PWID). METHODS: Prospective observational study including consecutive HCV RNA positive individuals attending a low-threshold clinic in Oslo, Norway, between 2013 and 2020. Participants were offered individually tailored HCV treatment and post-treatment HCV RNA surveillance at three months intervals. RESULTS: Of 488 HCV RNA positive individuals, 363 initiated treatment (median age 48.7 years, 72.5% male, 17.2% liver cirrhosis, 54.3% unstable housing). All participants had a history of injecting drug use, 71.1% received opioid agonist treatment, and 70.1% reported recent (past 3 months) injecting. In intention-to-treat analysis, excluding those with HCV RNA results pending, virologic response was achieved in 306 of 340 (90.0%) participants. In modified intention-to-treat analysis, also excluding those with loss to follow-up during treatment, virologic response was achieved in 306 of 323 (94.7%). Virologic response was not associated with recent injecting drug use or socio-demographic factors. Reinfection surveillance was accomplished in 297 individuals (308.2 PY of follow-up; median 0.50 years). Eight cases of reinfection were detected for an incidence of 2.60/100 PY (95% CI 1.12-5.11) overall, and 3.74/100 PY (95% CI 1.62-7.37) among those with injecting drug use during follow-up (n = 205). Reinfection was associated with younger age (IRR 0.37; 95% CI 0.18-0.74), and all cases occurred in participants aged below 49 years with ongoing injecting drug use who reported mixed heroin/amphetamine injecting. Successful retreatment was provided in all cases and no second reinfections were observed. CONCLUSION: The findings consolidate previous evidence supporting the effectiveness of HCV treatment among PWID, provide novel data on reinfection rates and associated factors, and demonstrate the feasibility of reinfection surveillance and retreatment in a real-world setting.