Syringe exchange and risk of hepatitis B and C in injection drug users

Research on needle exchange programs for injection drug users (IDUs) suggests that they may have multiple protective effects, including prevention of infection with blood-borne viruses and improving access to medical care and drug treatment services. In this study, incidence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection was examined in relation to participation in the Seattle exchange program. IDUs were recruited into a cohort study from 6/94 to 1/96, using a systematic sampling scheme. Subjects (187 who were seronegative for antibody to HCV, and 460 seronegative for core antibody to HBV) were followed for one year to observe seroconversion. There were 39 HCV infections, for a rate of 21.1 per 100 person-years at risk, and 46 HBV infections (10.4/100 person-years). Relative to non-users of the exchange, regular users during the follow-up had about a thirty percent increase in the rate of HCV infection (RR = 1.31). However, the confidence intervals around this estimate were wide (0.79-2.19), as were those around the even higher relative risk associated with sporadic exchange use (RR = 2.59; 0.79-8.5). The adjusted RR for HBV infection associated with regular exchange use was 1.8 (CL 0.69-4.77), with sporadic use, RR = 2.36 (0.86-6.47), and for former users, the RR was 0.7 (0.2-2.5).; In this study, where was no indication that use of the needle exchange was related to a reduced risk of HBV or HCV infection. Indeed, highest incidence occurred among current users of the needle exchange, even after adjustment for confounding variables. This suggests that new public health programs to address the problems of HBV and HCV control in IDUs are urgently needed.