PID12: AVERTING FUTURE AIDS CASES: MODELING COSTS OF INTERVENTIONS WITH OUT-OF-TREATMENT SUBSTANCE ABUSERS

Abstract

OBJECTIVE: The North Carolina Cooperative Agreement (NCCoOp) for AIDS Intervention Research implemented an AIDS intervention in an urban, high-risk, primarily African-American, crack and injection drug-using population. Estimated costs for the standard intervention are $242 per person. How many future AIDS cases will be averted by making this expenditure? METHODS: We constructed an epidemic model to assess the long-term impacts of intervention related changes on HIV incidence and prevalence. Our model is a dynamic compartment model focusing on 8 distinct sexual and drug use risk groups within the community. Cost data are available from existing intervention analyses. RESULTS: 778 persons were enrolled in the NCCoOp intervention in Wake and Durham counties, NC. Of these, 80 (11.5%) were HIV positive. Using data collected prior to intervention, our model predicts that HIV prevalence will rise to 18% of the NCCoOp population in five years. The epidemic is driven predominantly by high-frequency needle users (HFNU), primary needle users (PNU), and primary crack users (PCU) who account for 79% of new infections over this time period. Using data collected after intervention, our model predicts HIV prevalence will decline to 7% of the NCCoOp population in five years. However, HFNU, PNU, and PCU account for 89% of new infections in this case. Risky drug use and sexual behaviors were dramatically reduced by intervention and this accounts for most of the reduction in HIV prevalence. Other factors influencing the reduction in HIV prevalence are AIDS mortality and growth in the drug using population. CONCLUSIONS: Our model provides evidence than an effective AIDS intervention in a high-risk population of out-of-treatment substance abusers can avert significant numbers of new HIV infections, which may offset initial costs.