Modeling the Impact of Needle Exchange Programs Accounting for both HIV and HCV Infections and HIV/CV Co-Infections
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Purpose: The aim of this study is to model the impact of needle exchange interventions on human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Methods: In order to model the impact of needle exchange interventions, behavioural effects (sexual and drug use) were translated into estimates of the number of HIV and HCV cases averted by the programs through a mathematical model. Behavioural effects data on 63 clients had been collected previously by two Health Units in Ontario. The secondary data were analyzed to estimate the number of HIV and HCV cases averted while accounting for co-infection. A Bernoulli process model was used to estimate the number of averted cases for the condom distribution and counselling aspects of the needle exchange intervention. A modification of the Bernoulli process model was used for needle exchange interventions to account for drug use behaviours. Furthermore, this model estimated the number of cases averted while also accounting for the clients’ partner’s co-infection status. Once the number of HIV and HCV cases averted was determined, a cost analysis was conducted to estimate the net medical savings of the interventions. Costs were converted to 2011 Canadian dollars. Results: Of the 63 clients, 21.40 HIV and 5.18 HCV cases were directly averted by the needle exchange intervention when HIV/HCV co-infection status of the partner was not taken into account. When the clients’ partners’ co-infection status was taken into account, lesser numbers were directly averted by the needle exchange intervention. The discounted medical savings averted were $6,950,028 and $6,741,331 when co-infection was and was not accounted for, respectively, for the 63 individuals. Conclusion: The study demonstrated a different modeling method to account for HIV and HCV cases averted in the context of needle exchange. This study provides a foundation for future large scale cost-effectiveness studies.