Optimal, near-optimal, and robust epidemic control

In the absence of drugs and vaccines, policymakers use non-pharmaceutical interventions such as social distancing to decrease rates of disease-causing contact, aiming to reduce or delay the epidemic peak. Because these measures carry social and economic costs, they may only be maintainable for short periods. We derive the theoretically optimal strategy for using a time-limited intervention to reduce the peak prevalence of a novel disease in the classic Susceptible–Infectious–Recovered (SIR) model. We show that broad, easier-to-implement strategies can perform nearly as well as the optimal strategy. However, neither the optimal nor these near-optimal strategies are robust to implementation error: small errors in intervention timing can produce large increases in peak prevalence. Robust control requires a strong, early, and ideally sustained response.