. Sensitivity analyses show that including the potential for immunity has minimal effect on the predictions; prevalence reductions remain even if SVR is assumed to be 25% lower among active IDU than current evidence suggests; retreatment of treatment failures does not alter the short-term (<5 years) projections, but does increase treatment gains within 20 years; hepatitis C free life years gained from treating active injecting drug users are projected to be higher than from treating non-injecting drug users