HIV INCIDENCE AMONG INJECTING DRUG-USERS IN NEW-YORK-CITY SYRINGE-EXCHANGE PROGRAMS

Background There have been no studies showing that participation in pr ogrammes which provide legal access to drug-injection equipment leads to individual-level protection against incident HIV infection. We have compared HIV incidence among injecting drug users participating in sy ringe-exchange programmes in New York City with that among non-partici pants. Methods We used meta-analytic techniques to combine HIV inciden ce data from injecting drug users in three studies: the Syringe Exchan ge Evaluation (n=280), in which multiple interviews and saliva samples were collected from participants at exchange sites; the Vaccine Prepa redness Initiative cohort (n=133 continuing exchangers and 188 non-exc hangers, in which participants were interviewed and tested for HIV eve ry 3 months; and very-high-seroprevalence cities in the National AIDS Demonstration Research (NADR) programme (n=1029), in which street-recr uited individuals were interviewed and tested for HIV every 6 months. In practice, participants in the NADR study had not used syringe excha nges. Findings HIV incidence among continuing exchange-users in the Sy ringe Exchange Evaluation was 1 . 58 per 100 person . years at risk (9 5% CI 0 . 54, 4 . 65) and among continuing exchange-users in the Vacci ne Preparedness Initiative it was 1 . 38 per 100 person-years at risk (0 . 23, 4 . 57), Incidence among non-users of the exchange in the Vac cine Preparedness Initiative was 5 . 26 per 100 person-years at risk ( 2 . 41, 11 . 49), and in the NADR cities, 6 . 23 per 100 person-years at risk (4 . 4, 8 . 6). In a pooled-data, multivariate proportional-ha zards analysis, not using the exchanges was associated with a hazard r atio of 3 . 35 (95% CI 1 . 29, 8 . 65) for incident HIV infection comp ared with using the exchanges. Interpretation We observed an individua l-level protective effect against HIV infection associated with partic ipation in a syringe-exchange programme. Sterile injection equipment s hould be legally provided to reduce the risk of HIV infection in perso ns who inject illicit drugs.