Fig. 1. Model dynamics.

Four types of dynamics are modeled: infection, behavioral, vaccination, and population. Infection dynamics (thick black line) account for infection and recovery; behavioral dynamics (dotted black line) account for movement between the high and low sub-populations; vaccine dynamics (thin black line) account for the loss of vaccine protection; population dynamics (dashed grey line) account for entry to and exit from the population. Vaccine administration is assumed to occur just prior to sexual debut. Most parameters take sex-specific values (not shown; Supplemental materials summarize these details). Unvaccinated states include people who have never received the vaccine and also people previously vaccinated who have lost vaccine protection due to waning.