8th International AIDS Conference Amsterdam, Netherlands — July 19-24, 1992

Int Conf AIDS 1992 Jul 19-24; 8:We62 (abstract no. WeC 1092)
Kaplan EH, Heimer R; Yale School of Organization and Management, New Haven, CT.

OBJECTIVE: To verify our earlier prediction that HIV incidence has been reduced among IDUs in the New Haven needle exchange program.

METHODS: A syringe tracking and testing system (STT) was established whereby all needles distributed by the program receive unique tracking codes, and a sample of returned needles are tested for the presence of HIV proviral DNA using PCR. From the STT, it is possible to sequence chronologically the needles returned by individual IDUs in the program, and to statistically determine whether the infection pattern in the needles shifted from predominantly negative to predominantly positive during the course of the needle exchange, as would occur if the IDU in question became infected.

RESULTS: Earlier modeling predicted a drop in HIV incidence from 6.4 per 100 IDUs per year to 4.3 per 100 IDUs per year owing to the operation of the needle exchange. The data employed here covered the equivalent of 9,062 client days, thus one would expect 1.07 new infections to be discovered if the incidence of infection had been reduced as predicted, with a 95% Poisson coverage interval of 0-3 infections. PCR tests of 850 needles covering 69 client IDUs (for an average of 12.3 needles tested per IDU), were statistically analyzed four ways. Three of the analyses determined mean incidence levels falling inside the coverage interval (0.31, 0.55, 1.31), while the fourth fell just outside (3.55).

CONCLUSIONS: These data are consistent with the incidence reduction forecast earlier. That the technique employed here is completely different from Kaplan's "Needles That Kill" model on which earlier conclusions were based provides additional evidence that needle exchange has reduced HIV incidence in New Haven.

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