New developments and opportunities for preventing hepatitis C virus (HCV) among people who use and inject drugs-announcing an Addiction series.

We announce a new series for Addiction on HCV (hepatitis C virus). This is prompted by the changing treatment and prevention landscape and syndemic of HCV and drug use, specifically concerning people who inject drugs (PWID). In some developing countries more than 80% of HCV is among people with a history of drug injection; globally, almost 40% of HCV burden is attributable to injecting drug use and inmany countries one in two PWID are likely to be living with HCV [1–3]. HCV is an important cause of liver disease, along with alcohol, hepatitis B virus (HBV) and metabolic causes, and the only one that can be cured easily [4]. There is no vaccine available for HCV. However, new HCV anti-viral drugs—so-called direct-acting anti-virals (DAAs)—are highly tolerable, of short duration (8–12weeks) and can cure the disease in the vast majority of cases, with trials involving PWID reporting more than 90% cure rates [5–7]. These advancements have raised excitement around the possibility of using HCV treatment as Prevention (TasP). Globally, however, very few PWID are treated for their HCV. Although the cost of DAA therapies can be high, health economic models suggest that prioritizing PWID for early HCV treatment because of the prevention benefits is likely to be cost-effective [8]. In addition, there is strengthening empirical evidence that primary prevention interventions such as opioid substitution treatment (OST) and needle and syringe programmes (NSP) can reduce HIV and HCV [9–12]. However, theoretical model projections suggest that substantial reductions in HCV transmission among PWID will require both traditional harm reduction/primary prevention and HCV treatment scale-up [13,14]. The ease of administration of these new DAA therapies means that they could be delivered by non-specialists in the community and within drug treatment services, leading to the recommendation that HCV treatment, drug treatment and prevention services should be integrated, which may have advantages and disadvantages in the way that drug treatment services are delivered [15]. International clinical guidelines recommend that people at risk of transmitting HCV are treated for HCV [16–18]. The World Health Organization Global Health Sector Strategy (GHSS) on Viral Hepatitis has set a challenging goal of eliminating viral hepatitis as a major public health threat by 2030, reducing new chronic infections by 90% andmortality by 65%. Inmost countries these targets can be achieved only through scaling-up both OST, NSP and HCV treatment for PWID, as highlighted in a recent paper (the first in our series) on HCV in Greece [19]. Another model study in our series shows that managing HCV in prisons can make a substantial contribution to reducing transmission in the community [20]. Several countries, such as Australia, France, Georgia and Portugal, have already announced and started national HCV elimination campaigns, increasing the number of HCV treatments available and removing any restrictions on access [21,22]. There are great opportunities, therefore, to generate robust evidence on how to prevent HCV transmission and HCV-related morbidity in PWID and in the population. We expect, therefore, as a Commentary in this issue argues, to move from the ‘the theoretical to the empirical sphere’ [23]. While these are ambitious goals, success is not guaranteed. Reaching and engaging people with HCV are key challenges, given the prohibition surrounding illicit and injecting drug use and the resultant stigma and discrimination concerns and possible mistrust of health services. Community and peer involvement is likely to be critical to the success of HCV prevention programmes. It has also been hypothesized by some clinicians and researchers that successful treatment of HCV can improve recovery and engagementwith drug treatment services [24]. The purpose of our new series will be to highlight and document the best new evidence emerging from around the world on the syndemic of HCV and drug use. We are interested in receiving systematic reviews, trials and other evaluations, ethnographic and modelling studies that inform and test how HCV can be prevented in people who use and inject drugs.