An economic model of cost effectiveness of peer interventions to prevent HIV infections in prison.

Aim: To assess the cost-effectiveness of peer-based sexual behaviour education interventions in prison settings to prevent primary and secondary HIV infections. Methods: Based on the results of a systematic review of peer-based interventions in prison settings, we developed a Bernoulli model to estimate the number of HIV infections averted, consequent loss of quality-adjusted life years (QALYs) avoided and associated savings in health care costs over a lifetime respectively for a peer-led and a professionally-led education intervention. Results: The economic model showed that peer-led and professionally-led educational interventions prevent future HIV infections among offenders in prison settings, thus saving a significant amount of health care costs compared to a ‘do nothing’ scenario. In addition the peer-led intervention is dominant when compared to the professionally-led intervention (it is more effective and less costly). Whilst the model is surrounded by considerable uncertainty, the dominance scenario is confirmed in the one-way and probabilistic sensitivity analysis conducted. Conclusions: This study adds to previous evidence on the effectiveness of peer based educational interventions in preventing HIV in prison by showing that these are not only more effective but also cost less than the professionally-led alternative.