Backpack needle exchange: background, design, and pilot testing of a program in Rhode Island.

Many individuals who inject drugs do not access existing needle and syringe exchange programs. The ability to obtain clean needles from needle exchanges is limited by operational difficulties, the hours of operation, the location of the programs, and a lack of transportation. Providing multiple points of access to clean needles, including mobile exchange sites, may be necessary to prevent the transmission of the human immunodeficiency virus and other blood-borne viruses.