Fig 2. Program efficiency and policy domains of age-group prioritization in the voluntary medical male circumcision (VMMC) program.

A) Expansion path curve showing the incremental change in total cost of the VMMC program (program cost) relative to the incremental change in total number of HIV infections averted (magnitude of impact) for each age group- targeted scenario. The blue line shows the expansion of the program with minimal diminishing of returns, and the red line shows the expansion of the program with considerable diminishing of returns. B) Frontier policy plot delineating the different policy domains based on the theme of maximizing program efficiency (maximizing gain while minimizing cost). Circle size represents the total number of HIV infections averted (magnitude of impact). C) Frontier policy plot delineating the different policy domains based on the theme of maximizing the total impact of the VMMC program. Circle size represents the total number of VMMCs needed. In both B and C, the orange circles represent the age brackets that fit into the optimal policy domain, the red circles represent Zimbabwe’s current targeted age group (13–29 year old males), and the blue circle represents the baseline VMMC intervention scenario. * Gain/Pain index: the proportional reduction in the total number of infections averted (Gain) over the proportional reduction in the total VMMC program cost (Pain). These proportions are assessed relative to the baseline scenario of targeting males aged 15–49 years.