Of a total of 12.7 to 16 million people who inject drugs (PWID), an estimated 10 million are infected with hepatitis C virus (HCV).1 This grim statistic makes HCV the most prevalent infectious disease in PWID.2 Infection is primarily transmitted by sharing needles and syringes. Since HCV can survive outside of the human body for weeks, the high rate of transmission in a population sharing needles and syringes is not surprising.3
Two types of intervention are used to reduce HCV transmission in people who inject drugs: needle/syringe programs (NSPs) and opioid substitution therapy (OST).4 NSPs were introduced in the 1980s in an effort to control the global HIV epidemic through the use of sterile injection equipment in PWID.2 Since then, NSPs have been a critical component of efforts aimed at reducing or minimizing all drug-related harms and preventing blood-borne infections such as HIV, HBV, and HCV.
Implementing all aspects of NSPs — including education, behavioral modifications in PWID and providers, and distribution and continued access to sterile injecting equipment — is a complex task requiring cooperation between users, healthcare providers, and healthcare systems.2
In an interview with Infectious Disease Advisor, Lucy Platt, PhD, associate professor of public health epidemiology at the Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, United Kingdom, and Don C. Des Jarlais, PhD, professor of psychiatry and preventive medicine at the Icahn School of Medicine at Mount Sinai, New York, discussed the effectiveness of NSPs in preventing transmission of HCV.
Infectious Disease Advisor: How effective are the NSPs for preventing the acquisition of HCV in PWID?
Lucy Platt, PhD: Findings from our systematic review4 suggested that high coverage of NSPs resulted in a more than 50% reduction in HCV transmission in studies conducted in Europe, but studies in North America have shown little effect. This discrepancy may be related to the way NSP uptake is measured, as in Europe it is defined in terms of the people who receive 100% sterile syringes per injection (from any source), while in North America it is measured as frequency of NSP use. We know that people attending NSPs often have multiple social vulnerabilities; they are more likely to be homeless or inject crack cocaine, both factors that increase the risk for HCV infection. Less frequent use of NSPs in the United States may also mask an intervention effect.
Infectious Disease Advisor: Is a combination of opioid substitution therapy (OST) and NSP interventions more effective in reducing the risk for HCV acquisition?
Dr Platt: There was consistent and strong evidence that current use of opioid substitution therapy reduces the risk of hepatitis C infection by 50%, and, when combined with a high coverage NSP, reduces the risk by 74%. Therefore, our findings show the need to remove restrictions on the concurrent use of NSP and OST to maximize the reduction in HCV transmission. We found some evidence showing a differential impact of OST by sex: with every 10% increase in the percentage of women in a sample, the effect of OST was reduced. NSP and OST services need to develop policies and practices to encourage women to use services addressing gender-specific injection-related risk and other health and social welfare needs.
Infectious Disease Advisor: What types of studies still need to be conducted to gain a better understanding of the shortcomings of current NSPs and possible ways to improve them?
Dr Platt: The development of improved measures of NSP use, along with more consistent reporting of how studies are conducted, including the assessment of confounders, is needed to strengthen the evidence on the impact of NSPs.
More detailed assessments should examine service delivery and its cost-effectiveness in order to ensure that existing services are maintained and to promote the introduction and scale-up of services in countries and settings with emerging or growing epidemics of injection and opioid drug use. This line of research can shed light on the pathways between contextual factors and mechanisms of service delivery, and the extent to which these influence efficacy across different outcomes and settings. This is crucial given that HIV and HCV epidemics persist in Eastern Europe despite the implementation of OST and NSPs in some countries. Epidemics are also growing in countries in sub-Saharan Africa. OST is currently being implemented in Kenya and Tanzania, but there has been little formal evaluation of the different delivery models within the specific economic, social, and political contexts and the different epidemiology of HIV and HCV. This is necessary to inform an appropriate intervention response.
Infectious Disease Advisor: Dr Des Jarlais, you recently participated in an evaluation of the Community Health Outreach Work to Prevent AIDS (CHOW) project, the statewide syringe exchange program in Hawaii.5 Can you briefly explain the main goals and methods of the CHOW project, as they relate to the prevention of HIV and HCV acquisition in PWID?
Don C. Des Jarlais, PhD: The original purpose of the CHOW project was to prevent HIV infection in people who injected drugs in Honolulu through syringe exchange. The project has expanded to all of the major islands in the state and has become a multi-service program, providing HCV prevention, HIV and HCV testing, referral for treatment, and placement in substance use treatment programs. The CHOW project has been successful in limiting HIV transmission in PWID in Hawaii, keeping HIV prevalence low — less than 3%.
Infectious Disease Advisor: From your evaluation of the CHOW project results,5 how effective was the needle/syringe exchange program in preventing HCV acquisition in the studied population of PWID?
Dr Des Jarlais: HCV is much more transmissible than HIV, and the CHOW project has been only moderately effective in reducing HCV transmission in PWID in Hawaii. There was an extremely high prevalence of HCV in subjects in the study who began injecting prior to implementation of the project — approximately 90% — while in subjects who began injecting after the project was implemented there was up to an approximately 70% prevalence. The spline knot at 50 years of age indicates a change in the likelihood of acquiring HCV in people likely to have begun injecting before the project began. However, HCV prevalence in PWID in Hawaii is still unacceptably high and additional efforts at reducing HCV transmission are needed.
Infectious Disease Advisor: Which important factors influence the effectiveness of needle/syringe exchange programs in preventing blood-borne infections such as HCV?
Dr Des Jarlais: There are several factors that have contributed to the success of the CHOW project in Hawaii: beginning the program early, before HIV had spread widely in the PWID population; the dedication of the outreach workers and their skills in establishing trusting relationships with persons injecting drugs; strong community support, including support from the state government and law enforcement; a series of talented program directors; and a requirement for an annual evaluation, which generated data for continuous program improvement.
- World Health Organization (WHO). Guidance on prevention of viral hepatitis B and C among people who inject drugs. Reviewed July 2012. Accessed October 2, 2017.
- Fernandes RM, Cary M, Duarte G, et al. Effectiveness of needle and syringe programmes in people who inject drugs—An overview of systematic reviews. BMC Public Health. 2017;17:309.
- Leicht A. Improving the quality of needle and syringe programmes: an overlooked strategy for preventing hepatitis C among people who inject drugs. BMC Infect Dis. 2014;14(S6):S8.
- Platt L, Minozzi S, Reed J, et al. Needle syringe programmes and opioid substitution therapy for preventing hepatitis C transmission in people who inject drugs [published online September 18, 2017]. Cochrane Database Syst Rev. doi:10.1002/14651858.CD012021.pub2
- Salek TP, Katz AR, Lenze SM, et al. Seroprevalence of HCV and HIV infection among clents of the nation’s longest-standing statewide syringe exchange program: A cross-sectional study of Community Health Outreach Work to Prevent AIDS (CHOW). Int J Drug Policy. 2017;48:34-43.