Changes in injection risk behavior associated with participation in the Seattle needle-exchange program

We studied the influence of the Seattle, Washington, needle-exchange progra m on sharing of drug injection equipment (syringes, drug cookers, filtratio n cotton) to identify potential gaps in risk reduction and to understand in greater detail the lack of an association between exchange use and risk of hepatitis B or C virus transmission. In a cohort of 2,208 injection drug u sers who completed a 1-year follow-up visit, we measured the association be tween needle-exchange use at study enrollment lever vs. never and injection risk behavior at the follow-up. Control for confounding was tarried out us ing both logistic regression and propensity score analytic methods to estim ate the adjusted odds ratio (AOR). In both univariate and multivariate anal yses, needle-exchange use was associated with a lower likelihood of injecti on with a used syringe (AOR = 0.7, 95% confidence Limit 0.5, 0.9). There wa s no association between exchange use and cooker or cotton sharing (AOR = 0 .8, 95% confidence limit 0.6, 1.1) or between exchange use and use of a com mon syringe to divide drugs (AOR = 0.9). This analysis suggests that risk r eduction measures adopted by users of the Seattle exchange may not be suffi cient to prevent transmission of all blood-borne viruses, including hepatit is C virus. Greater awareness of the infection risk associated with these p ractices may help curb this type of equipment sharing and ultimately preven t disease transmission.