Suppressive valacyclovir therapy: impact on the population spread of HSV-2 infection.

Objectives: Recent trial results demonstrate that the transmission probability of HSV-2 in monogamous couples is nearly halved by the use of valacyclovir as suppressive therapy.

Goal: The goal of this study is to understand the potential impact of suppressive valacyclovir therapy on the transmission of HSV-2 within a population.

Study Design: A mathematical model of HSV-2 epidemiology was developed which included suppressive therapy with the efficacy observed in the clinical trial. The model represented HSV-2 spread in an age and sexual activity stratified population where rates of viral shedding declined based on time since infection. The model tested the impact of a range of suppression coverage levels.

Results: Suppressive therapy reduces the population incidence of HSV-2. With coverage rates of 3.2%, the incidence of HSV-2 would be reduced by between 1.8% and 2.8%. Higher coverage rates were estimated to reduce the incidence of new cases up to 13%. Starting suppression closer to the time of infection also reduces the incidence of new cases.

Conclusion: The impact of suppressive therapy on the HSV-2 epidemic is modest at current coverage levels but could be substantially increased with higher rates of diagnosis and a focus on coverage soon after infection.