For mitigating the COVID-19 pandemic, much emphasis is made on implementing non-pharmaceutical interventions to keep the reproduction number below one. However, using that objective ignores that some of these interventions, like bans of public events or lockdowns, must be transitory and as short as possible because of their significant economic and societal costs. Here, we derive a simple and mathematically rigorous criterion for designing optimal transitory non-pharmaceutical interventions for mitigating epidemic outbreaks. We find that reducing the reproduction number below one is sufficient but not necessary. Instead, our criterion prescribes the required reduction in the reproduction number according to the desired maximum of disease prevalence and the maximum decrease of disease transmission that the interventions can achieve. We study the implications of our theoretical results for designing non-pharmaceutical interventions in 16 cities and regions during the COVID-19 pandemic. In particular, we estimate the minimal reduction of each region’s contact rate necessary to control the epidemic optimally. Our results contribute to establishing a rigorous methodology to design optimal non-pharmaceutical intervention policies for mitigating epidemic outbreaks.

为了缓解 COVID-19 大流行，非常重视实施非药物干预措施，以将传染数控制在 1 以下。然而，使用这一目标忽略了其中一些干预措施，如禁止公共活动或封锁，必须是暂时的，并且尽可能短，因为它们会产生巨大的经济和社会成本。在这里，我们得出了一个简单且数学上严格的标准，用于设计缓解流行病爆发的最佳暂时性非药物干预措施。我们发现将繁殖数降低到 1 以下就足够了，但不是必需的。相反，我们的标准根据期望的最大疾病流行率和干预措施可以实现的最大疾病传播减少来规定所需的繁殖数量减少。我们研究了我们的理论结果对于在 COVID-19 大流行期间在 16 个城市和地区设计非药物干预措施的影响。特别是，我们估计了最佳控制疫情所需的每个地区接触率的最小减少量。我们的研究结果有助于建立严格的方法来设计最佳的非药物干预政策以减轻流行病的爆发。