Effectiveness and Cost-Effectiveness of Treatment as Prevention for HIV

Excerpt

The beneficial effects of antiretroviral therapy (ART) on individual health are well established, and ART is widely used to reduce the morbidity and mortality due to the human immunodeficiency virus (HIV) (WHO 2016). Recent evidence has strengthened the case for initiating ART as early in the disease stage as possible (Danel and others 2015; INSIGHT START Study Group 2015). Similarly, using ART to prevent mother-to-child transmission of HIV is supported with conclusive evidence and has been adopted into clinical policies worldwide, as discussed in chapter 6 of this volume (John-Stewart and others 2017). Years of accumulating biological and observational evidence also suggest that ART may reduce sexual transmission of HIV, although the field lacked conclusive evidence until recently (Donnell and others 2010; Nachega and others 2013).

The evidence base and attention to “treatment as/for prevention” strengthened substantially in 2011 with the interim results from HIV Prevention Trials Network (HPTN) 052, a randomized controlled trial of early versus delayed use of ART among serodiscordant couples (Cohen and others 2011). The trial demonstrated a 96 percent reduction in new infections with earlier initiation of ART and provided strong evidence that ART reduces the sexual transmission of HIV. Final results of this trial with nearly 10,000 person-years of follow-up with similar conclusions were published in 2016 (Cohen and others 2016).

This emerging evidence stimulated a range of questions regarding the biological mechanisms of HIV treatment as prevention (TasP), variations in efficacy across subgroups, differences in at-risk populations, optimal implementation strategies, and potential implications for public health (Cohen, Holmes, and others 2012; Delva and others 2012). Recognition of the dual benefits of treatment has resulted in the reevaluation of the cost-effectiveness of ART, as well as of the paradigms of HIV prevention (Garnett and others 2017) and has led to policy discussions about how best to value the risks and benefits of treatment for personal and public health.

Even as substantial research and evaluation have improved the understanding of these trade-offs, clinical and public health policy and funding decisions are being made at the program, national, and global levels. This chapter examines the concept of HIV TasP, focusing on the underlying biological mechanisms, effectiveness, and cost-effectiveness of various strategies and settings and assessing how these factors may influence resource allocation, policy decisions, and research agendas at the national and global levels.