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Canada Communicable Disease Report

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Volume: 27S3 • September 2001

Viral Hepatitis and Emerging Bloodborne Pathogens in Canada

The Effectiveness of Harm Reduction Strategies in Modifying Hepatitis C Infection among Injection Drug Users in Canada

Lynne Leonard, Christine Navarro, Linda Pelude, Leslie Forrester


Populations with high levels of exposure to potentially infected blood are at the highest risk of being infected with HCV. Injection drug users (IDUs) are primarily at risk of HCV infection when they inject with previously used needles and syringes contaminated with the infected blood of another user. In addition, they are at increased risk when they share other contaminated injecting equipment, such as spoons, cookers, or cotton filters. It has been estimated that the average prevalence of HCV among IDUs in Canada is approximately 80%(1-7).

Injection drug use is currently the most important risk factor for HCV infection. In Canada, it accounted for 63.2% of acute hepatitis C cases with known risk factors identified through HC's Enhanced Surveillance System for Hepatitis B and Hepatitis C, for the period 1998-1999. Moreover, 77.8% of the IDUs who were interviewed under this system, reported having shared needles in the 6 months before diagnosis.

HCV may be a more serious threat to IDUs than either HBV or HIV. Persistent HCV infection develops in up to 85% of those acutely infected, whereas less than 10% of adults who become infected with HBV develop a chronic infection. Although persistence is even higher for HIV, the reservoir of HIV-infected IDUs is smaller(8), and HIV is less easily transmitted parenterally than HCV. Thus, the high prevalence, the high rate of persistent infection, and the high transmissibility of HCV all contribute to its endemicity in this group. Combined with the high rates of long-term sequelae, HCV among IDUs is of major public health importance(9).

The harm reduction framework

In 1987, the Canadian government adopted harm reduction as the framework for Canada's National Drug Strategy(10). The objective of the harm reduction approach is to reduce the harm associated with injection drug use to the individual, the community, and society as a whole. The economic, social and health-related consequences of injection drug use rather than its elimination are the focus of harm reduction strategies(10). Numerous international examples of harm reduction programs and policies exist and include needle exchange programs (NEPs), methadone maintenance treatment (MMT) programs as well as educational and outreach programs. For many, NEPs exemplify the harm reduction approach. The rationale behind NEPs is that the provision of sterile needles and syringes to current injectors will help to reduce the risk of infection or transmission of HIV, HBV, HCV, and other bloodborne pathogens. In Canada, NEPs opened unofficially in Toronto in 1987, and officially in Vancouver in 1989. There are now more than 200 NEPs operating across Canada(11). Although evidence exists that NEPs have been effective in modifying most HIV-related injection practices(12) it cannot be assumed that HIV-harm reduction strategies have been equally effective in addressing HCV in IDUs(13).

The effectiveness of harm reduction

The present paper provides a summary of a systematic review, the principal objectives of which were to document and characterize the prevalence and incidence rates of HCV among IDUs in Canada, and to examine the effectiveness of harm reduction strategies in modifying these rates(14). HCV-related outcomes of interest were end-point physical health status at either the population or individual level, including modification in the reported incidence and prevalence of HCV among IDUs.

On-line computer searches of six electronic databases, hand searches of relevant studies, examination of potentially relevant studies suggested by key informants at the federal and front line levels, and review of local and community publications resulted in the retrieval of 84 studies from 1990 to 2000 related to the effectiveness of harm reduction strategies. A review of the relevance and quality of the studies resulted in the inclusion of 15 relevant* but largely methodologically weak primary studies, none of which was Canadian. It is important to note that not one of the studies examined had the express objective of directly evaluating harm reduction strategies in terms of HCV.

Of the 15 studies, three were American, three were Australian, and nine were European. The studies varied in the number of IDUs participating (range from 46 to 673) and composition of the IDU population. Although all studies recruited IDUs as at least one component of the study population, one study was composed exclusively of the inmates of a small prison for women in Switzerland(15), and one study focused on heterosexual IDUs only(16). In all studies, with the exception of the study of women inmates, the proportion of male IDUs to female IDUs was approximately two-thirds to one-third, a ratio frequently documented in studies of IDUs. In terms of the interventions described, little similarity was observed across studies. NEPs and MMT were the most prevalent types of intervention described. One Scottish(17) and two U.S. studies(16,18) described NEPs as their only intervention, whereas MMT was the only intervention described in one Swiss(19), one Australian(20), and one Italian study(21). The remaining nine studies described multi-faceted harm reduction interventions, including any combination of NEPs, MMT and other forms of drug treatment, education, counselling, prevention, and community outreach.**

With regard to the effectiveness of harm reduction strategies in reducing the incidence and prevalence of HCV, the studies reviewed reported high rates of HCV prevalence and incidence despite apparent widespread implementation of prevention strategies. More specifically, it was observed that the earlier protective effect of NEP attendance against HCV seroconversion, as reported by Hagan and colleagues in 1995(16), has not been consistently sustained(18). Similarly, although a marginally protective role of MMT in the control of HCV infection was reported by Rezza and colleagues(21), this was not supported in any of the other studies reviewed, suggesting that the simple provision of methadone to IDUs at risk of HIV infection or of HIV transmission is not necessarily effective against HCV transmission.

Absence of a decline in incidence, or even the presence of incident cases, among IDUs already attending a prevention setting, albeit primarily focused on prevention of HIV transmission, strongly suggests that current efforts aimed at the prevention of bloodborne viral transmission are inadequate to stem HCV infection. Results from the studies reviewed document incidence rates ranging from a low of 4.2 per 100 person-years in a private Swiss MMT Centre(22) to highs of 20.9 per 100 person-years among IDUs attending a well-established HIV prevention facility in Australia(23) and 28.6 per 100 person-years among IDUs attending one of three drug treatment centres in Naples, Italy(21).

In summary, evidence from these primary studies suggests that HIV prevention strategies have been relatively ineffective in preventing HCV infection in the IDU population. Although harm reduction measures have contributed to the maintenance of a low prevalence and incidence of HIV, transmission of HCV clearly continues at extremely high levels, and from the evidence from many of the studies reviewed, this is particularly true among younger IDUs.

These findings, however, need to be considered in the context of certain limitations. As observational studies, none of the studies examined had the express objective of directly evaluating harm reduction strategies in relation to HCV infection. To determine the effectiveness of such strategies in modifying levels of HCV infection, a longitudinal design with a large number of IDUs randomly assigned to receive the intervention and others to receive no intervention together with a significantly high seroconversion rate over time would be necessary. Ethical and legal considerations preclude implementation of such an experimental study design in the face of evidence of effectiveness in relation to the prevention of HIV transmission. In addition, the review considered effectiveness in terms of modifying end-point measures of HCV prevalence and incidence. Emphasis on these end-point outcomes may well have masked the effectiveness of the programs and strategies reviewed in terms of modifying intermediate measures towards declines in HCV incidence and prevalence. An example of this would be a lower level of engagement in HCV-related risk behaviours, such as the use of previously used needles and other injection equipment.

Elimination versus reduction of risk behaviours

High HCV prevalence and incidence rates have been reported in a number of studies despite apparent widespread implementation of risk reduction strategies that appear to have been adequate to maintain a low or lower prevalence of HIV. In particular, HCV seroconversion among attenders of harm reduction programs suggests that prevention directed selectively against HIV transmission is only partly effective in preventing HCV infection among IDUs. Public health measures to reduce HIV risk-related injection behaviours have had an impact on HIV transmission. However, in view of the documented large reservoir of existing HCV infection in the IDU population and the high degree of infectivity and transmissibility of HCV per episode of blood contact compared with HIV, research should be conducted to examine the feasibility of modifying existing programs or developing new ones that target the elimination rather than reduction of HCV risk-related injection behaviours. For instance, research could be carried out to examine the utility of interventions aimed at encouraging transitions to relatively less risky non-parenteral forms of drug ingestion such as smoking, snorting and swallowing. Similarly, research could be conducted to examine the effectiveness and feasibility of implementing MMT programs that administer methadone at the highest levels of the dose-response gradient associated with completed cessation of injecting, rather than simply reducing HCV risk-related injection practices. Establishing that HCV infection among IDUs is an important and high priority public health issue is fundamental to further interventions to control the spread of HCV.

References

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  5. Patrick DM, Cornelisse PG, Sherlock CH et al. Hepatitis C prevalence and incidence in Vancouver IDUs during an outbreak of HIV infection [Abstract #13296]. International Conference on AIDS 1998;12:145.

  6. Strathdee SA, Patrick DM, Currie SL et al. Needle exchange is not enough: lessons from the Vancouver injecting drug use study. AIDS 1997;11(8):F59-F65.

  7. Stratton E, Lior LY, Gully P et al. HIV, HBV and HCV risk behaviours in a semi-rural community in Canada [Abstract #23219]. International Conference on AIDS 1998;12:385.

  8. Villano SA, Vlahov D, Nelson KE et al. Incidence and risk factors for hepatitis C among injection drug users in Baltimore, Maryland. J Clin Microbiol 1997;35(12):3274-77.

  9. Crofts N, Hopper JL, Bowden DS et al. Hepatitis C virus infection among a cohort of Victorian injecting drug users. Med J Australia 1993;159(4):237-41.

  10. Canadian AIDS Society. Under the influence: making the connection between HIV/AIDS and substance abuse. Ottawa, ON: Canadian AIDS Society, 1997.

  11. Riley D. Drug policy and HIV/AIDS. Canadian HIV/AIDS Policy & Law Newsletter 1996;2(4).

  12. Leonard L, Forrester L, Navarro C et al. The effectiveness of needle exchange programmes in modifying HIV-related outcomes: a systematic review of the evidence, 1997-1999. Prepared for the Effective Public Health Practice Project of the Public Health Branch, Ontario Ministry of Health, 1999.

  13. Wodak A, Crofts N. HIV revisited: preventing the spread of blood-borne viruses among injecting drug users. Australian J Public Health 1994;18(3):239-40.

  14. Leonard L, Navarro C, Pelude L. Injection drug use and hepatitis C in Canada: the effectiveness of harm reduction strategies. A systematic review of the evidence 1990-2000. Report prepared for Bloodborne Pathogens Division, Health Canada, Ottawa, 2000.

  15. Nelles H, Bernasconi S, Dobler-Mikola A et al. Provision of syringes and prescription of heroin in prison: the Swiss experience in the prisons of Hindelbank and Oberschongrun. Int J Drug Policy 1997;8(1):40-52.

  16. Hagan H, DesJarlais DC, Friedman SR et al. Reduced risk of hepatitis B and hepatitis C among injection drug users in the Tacoma Syringe Exchange Program. Am J Public Health 1995;85(11):1531-37.

  17. Goldberg D, Cameron S, McMenamin H. Hepatitis C virus antibody prevalence among injecting drug users in Glasgow has fallen but remains high. Commun Dis Public Health 1998;1(2):95-7.

  18. Hagan H, McGough JP, Thiede H. Syringe exchange and risk of infection with hepatitis B and C viruses. Am J Epidemiol 1999;149(3):203-13.

  19. Chamot E, de Saussure PH, Hirschel B. Incidenceof hepatitis C, hepatitis B, and HIV infections among drug users in a methadone maintenance programme. AIDS 1992;6:431-32.

  20. Crofts N, Nigro L, Oman K et al. Methadone maintenance and hepatitis C infection among injecting drug users. Addiction 1997;92(8):999-1005.

  21. Rezza G, Sagliocca L, Zaccarelli M et al. Incidence rate and risk factors for HCV seroconversion among injecting drug users in an area with low HIV seroprevalence. Scandinavian J Infect Dis 1996;28:27-9.

  22. Boers B, Junet C, Bourquin M et al. Prevalence and incidence rates of HIV, hepatitis B and C among drug users on methadone maintenance treatment in Geneva between 1988 and 1995. AIDS 1998;12(15):2059-66.

  23. Van Beek I, Dwyer R, Dore GJ et al. Infection with HIV and hepatitis C virus among injecting drug users in a prevention setting: retrospective cohort study. BMJ 1998;317 (7156):433-7.

* The precise methodology, including search strategy, relevance testing for study selection, and quality testing of relevant studies is documented in the full review article(14).

** A complete description of the interventions in terms of modes of program delivery, duration, consistency, and setting is documented in the full review article(14).

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