The impact of HIV treatment as prevention in the presence of other prevention strategies: Lessons learned from a review of mathematical models set in resource-rich countries

Objective We aimed to assess the potential prevention benefits of HIV treatment as prevention (TasP) in resource-rich countries and examine the potential interactions between TasP and other prevention strategies by reviewing mathematical models of TasP. Method Multiple databases were searched for mathematical models published in the previous 5 years (from July 2007 to July 2012). The nine models located were set in Canada, Australia and the United States. Results These models' predictions suggested that the impact of expanding treatment rates on expected new infections could range widely, from no decrease to a decrease of 76%, depending on the time horizon, assumptions and the form of TasP modeled. Increased testing, reducing sexually transmitted infections and reducing risky practices were also predicted to be important strategies for decreasing expected new infections. Sensitivity analysis suggests that current uncertainties such as the effectiveness of highly active antiretroviral therapy outside of heterosexual transmission, less than ideal adherence, and risk compensation, could impact on the success of TasP at the population level. Conclusion The results from large scale pilots and community randomized controlled trials will be useful in demonstrating how well this prevention approach works in real world settings, and in identifying the factors that are needed to support its effectiveness.