Svilen Konov, HIV i-Base

This model evaluates Highly Active Antiretroviral Therapy (HAART) as an intervention to reduce HIV incidence and prevalence in IDU communities. The model used is a network model based on a Mover-Stayer framework and on a previous cellular automaton model to evaluate HAART as prevention.

In the model, IDU are distinguished based on syringe-sharing behavior and HIV status, and exert social influence on peers, encouraging, or discouraging syringe sharing. HAART is applied at coverage levels of 0% to 100%, assuming complete adherence and no drug resistance, tracked HIV incidence, and prevalence to equilibrium. Community composition, needle sharing frequency (60/month), and initial HIV prevalence (31%) were derived from data on IDU enrolled in the Vancouver Injection Drug User Study (VIDUS). Published transmission rates for HIV disease stages were used. HAART, initiated after 5 years (Scenario 1), was combined with reduced risk behavior (Scenario 2), the latter repeated with HAART initiated after 1 year (Scenario 3).

Without intervention (Table 3), HIV spreads rapidly and reaches very high prevalence (90%) in the model. With increasing HAART coverage, HIV incidence and prevalence decrease for all scenarios, eventually reaching 0%. Without change in risk behavior (Scenario 1), HIV prevalence decreased gradually to 60% HAART coverage, dropping rapidly thereafter. Behavioral interventions (Scenarios 2 & 3) amplified HAART effects. At 40% to 50% HAART, both incidence and prevalence were reduced by about half. Above 80% coverage, the epidemic was effectively eliminated. Early HAART initiation showed little impact.

Table 3: Effect of HAART coverage on HIV incidence and prevalence in a network model of injecting drug users

Ref: Bastani P et al. Highly active antiretroviral therapy eliminates HIV epidemics in a network model of an Injecting Drug User community. Poster abstract 997.

http://www.retroconference.org/2010/Abstracts/38240.htm