A therapeutic HIV vaccine: how good is good enough?

The goal of a therapeutic HIV vaccine is to attenuate HIV disease progression in those already infected. Our objective was to establish comparative efficacy and cost-effectiveness thresholds at which a therapeutic vaccine would make a valuable contribution to HIV care. Using an HIV computer simulation model, we compared therapeutic vaccination with HIV standard of care without vaccination. Input data were obtained from the literature. Base case and sensitivity analyses related to vaccine magnitude, penetrance, durability, and cost. In the base case (0.5 log magnitude, 25% penetrance, 3-year durability, and US$ 4000 per series), vaccination increased quality-adjusted life expectancy (QALE) by 0.50 months compared to no vaccination (cost-effectiveness ratio US$ 89,900 per quality-adjusted life year (QALY)). Increasing vaccine penetrance to 50% increased the projected QALE benefit to 0.91 months (cost-effectiveness ratio US$ 45,500/QALY). Even modestly effective therapeutic HIV vaccines may produce small but meaningful increases in life expectancy and compare favorably to alternative uses of scarce HIV care resources.