Changes in hepatitis C virus prevalence and incidence among people who inject drugs in the direct acting antiviral era.

BACKGROUND: The World Health Organization (WHO) has set a goal to eliminate hepatitis C virus (HCV) infection by 2030, including a 90% reduction of HCV incidence. With the introduction of a needle syringe program (NSP) in Stockholm, Sweden, and unrestricted availability of direct acting antiviral (DAA) treatment, we investigate the change of prevalence and incidence of HCV infection among people who inject drugs (PWID) over time.

METHODS: All persons attending the Stockholm NSP 2013-2021 (n=4,138) were included. The prevalence of viremic HCV infection was investigated yearly. For incidence analysis, PWID at risk with at least one follow-up test were included. Participants were divided into naive defined as anti-HCV negative (n=791), and exposed, defined as anti-HCV positive with a negative HCV RNA (n=1,030). Risk factors for HCV infection were analyzed using parametric exponential proportional hazards regression models.

RESULTS: The prevalence of viremic HCV infection decreased from 62% to 30% year 2013-2021 while the prevalence of cured after treatment increased from 0 to 22%, corresponding to 42% cured after treatment out of eligible in 2021. The overall incidence rate in naive was 16.9 (95% CI 15.0-19.0) and in exposed 12.8 (95% CI 11.6-14.2) per 100 person years (PY) and was not significantly reduced years 2013-2015 to 2020-2021 in either group. Risk factors for incident HCV infection in multivariable analysis were sharing needles/syringes, younger age, custody/prison past year, and homelessness, whereas opioid agonist treatment was protective.

CONCLUSION: The prevalence of HCV was halved in PWID as unrestricted DAA treatment became available and NSP was established in Stockholm. However, overall incidence was not reduced. To meet the WHO incidence goal, targeting PWID with high injection risk behaviors for testing and treatment is essential, along with engagement in harm reduction services.