Needle-exchange participation, effectiveness, and policy: syringe relay, gender, and the paradox of public health.

Needle-exchange programs (NEPs) have been politically controversial, and most studies have focused on evaluating their effectiveness on human immunodeficiency virus (HIV) transmission rates with little emphasis on the process of how they are used. This article shows that the way intravenous drug users use NEPs may influence their effectiveness. Using data from Baltimore's NEP, participants (N = 2,574) were classified as low, medium, and high users based on the volume, frequency, and duration of contact with the NEP. Higher NEP use was associated with shorter syringe circulation times and less syringe relay, returning syringes to the NEP originally acquired by someone else. For a subsample that was HIV tested (N = 262), syringe relay among women was associated with HIV seroconversion (at a 95% confidence interval). We conclude that exclusive use of the NEP (no relay) provides greater HIV protection than NEP use involving syringe relay. The paradox is that public health goals will not be achieved by prohibiting syringe relay activities and promoting exclusive use. NEPs should broaden their education efforts to have participants understand the value of repeated visits to the NEP.