Panel 1: Model terms and definitions.

Model terms	Definitions
Fixed regimen	PrEP pills taken at regular intervals (daily or weekly)
On-demand regimen	PrEP pills taken before and after sex acts
Optimal PrEP assignment	On-demand PrEP was assigned if it resulted in i) any improvement in effectiveness with fewer pills taken than daily PrEP (Criterion 1); ii) more than 10 percentage points (pp) improvement in effectiveness compared to daily PrEP (Criterion 2); or iii) less than 10 pp reduction in effectiveness compared to daily PrEP with fewer than half the number of pills taken (Criterion 3). In all other cases daily PrEP was assigned.
Adherence-based PrEP assignment	Agents with adherence to daily PrEP below 40, 50, or 60% were assigned on-demand PrEP. All other agents were assigned to daily PrEP.