On Fast Multi-Shot COVID-19 Interventions for Post Lock-Down Mitigation

Fast intermittent lock-down intervals with regular period are suggested as a COVID-19 exit strategy from the widely adopted policy of total lock-down. Many proposed exit strategies have risks and uncertainties which could lead to a second wave of infection [1,2]. We demonstrate that our proposed policies have the potential to be a method of virus suppression, while at the same time allowing continued (albeit reduced) economic activity. Furthermore, these policies, while not eliminating the virus, can nevertheless be sustained over long periods of time, until a vaccine or treatment becomes available. The robustness of these policies stems from the fact that they are open loop methods; namely, lock-down periods are not triggered by measurements -- inevitably uncertain and delayed -- over short time scales such as hospital admissions, but rather are driven by predictable, high-frequency, periodic triggers in- and out- of lock-down. A slow and inherently robust outer supervisory feedback loop, based on measurements over longer time scales, is used to tune the parameters of the mitigation strategy. These methods can act alone, or can be used in combination with other mitigation strategies, to provide additional levels of effectiveness in their operation.