COVID-19: Fast multi-shot epidemic interventions for post lockdown Covid-19 mitigation: Open-loop mitigation strategies

这一为期4个月的冲刺的目标是设计和验证新的退出策略，即在允许重大经济活动的同时，积极抑制新冠肺炎的当前封锁政策。目前提出的退出策略表明，在找到有效疫苗之前，除了接触者追踪、掩蔽和其他措施外，可能还需要间歇性封锁。其中大多数建议使用数据驱动的反馈信号，如医院入院，以启动封锁，一个关键的设计考虑因素是医疗系统的容量。这种方法的困难在于时机问题。太早干预，人们只会将患病人数的高峰转移到较晚的日期，而太晚的干预不会限制感染人数的高峰。这种病毒的潜伏期长达14天，最初的指数增长率使时间问题变得更加严重。因此，在面临指数增长的情况下观察流行病的真实状态的问题，使任何数据驱动的反馈政策的有效性对干预的时机极为敏感。从经典的观点来看，控制具有时变时滞的局部不稳定系统是控制工程中的一个前沿问题。我们的建议是通过在短时间内开发周期性的开环锁定策略来绕过这一困难。这些政策将有助于抑制病毒，并允许可预见的周期性封锁，从而促进经济活动。这些政策将在先进、现实的流行病学数学模型和数据上得到验证，并将针对国家和国际区隔情景而制定。

The objective of this 4-month SPRINT is to design and validate new exit-strategies from the current lockdown policy that actively suppress COVID-19, while allowing significant economic activity. Currently proposed exit-strategies suggest that intermittent lockdowns, in addition to contact tracing, masking, and other measures, may be necessary until an effective vaccine is found. Most of the these propose using data-driven feedback signals, such as hospital admissions, to initiate lockdowns, with a key design consideration being the capacity of the healthcare system. The difficulty with this approach is timing. Intervene too early, and one simply shifts the peak of ill people to a later date, whereas too late an intervention will not limit the peak of infections. The issue of timing is exacerbated by the virus having up to a 14-day incubation period and an initial exponential growth rate. Thus, the problem of observing the true state of the epidemic, in the face of exponential growth, makes the effectiveness of any data-driven feedback policy extremely sensitive to the timing of intervention. From a classical perspective, controlling locally unstable systems, as this is, with time-varying time-delays, is known to be a frontier problem in control engineering. Our suggestion is to circumvent this difficulty by developing periodic open-loop lockdown strategies over short timescales. Such policies, will help suppressing the virus and allow predictable periodic periods of lockdown, thereby facilitating economic activity. The policies will be validated on advanced, realistic epidemiological mathematical models and data, and will be developed for national and international compartmental scenarios.