Saad-Roy Chadi M, Levin Simon A, Metcalf C Jessica E, Grenfell Bryan T
Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
J R Soc Interface. 2021 Feb;18(175):20200683. doi: 10.1098/rsif.2020.0683. Epub 2021 Feb 3.
SARS-CoV-2 is an international public health emergency; high transmissibility and morbidity and mortality can result in the virus overwhelming health systems. Combinations of social distancing, and test, trace, and isolate strategies can reduce the number of new infections per infected individual below 1, thus driving declines in case numbers, but may be both challenging and costly. These interventions must also be maintained until development and (now likely) mass deployment of a vaccine (or therapeutics), since otherwise, many susceptible individuals are still at risk of infection. We use a simple analytical model to explore how low levels of infection, combined with vaccination, determine the trajectory to community immunity. Understanding the repercussions of the biological characteristics of the viral life cycle in this scenario is of considerable importance. We provide a simple description of this process by modelling the scenario where the effective reproduction number [Formula: see text] is maintained at 1. Since the additional complexity imposed by the strength and duration of transmission-blocking immunity is not yet clear, we use our framework to probe the impact of these uncertainties. Through intuitive analytical relations, we explore how the necessary magnitude of vaccination rates and mitigation efforts depends crucially on the durations of natural and vaccinal immunity. We also show that our framework can encompass seasonality or preexisting immunity due to epidemic dynamics prior to strong mitigation measures. Taken together, our simple conceptual model illustrates the importance of individual and vaccinal immunity for community immunity, and that the quantification of individuals immunized against SARS-CoV-2 is paramount.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）构成国际公共卫生紧急事件；其高传播性以及发病率和死亡率可能导致病毒压垮卫生系统。社交距离措施以及检测、追踪和隔离策略相结合，可将每名感染者的新增感染数降至1以下，从而推动病例数下降，但这些措施可能既具有挑战性又成本高昂。在研发出疫苗（或治疗方法）并（目前很可能）大规模部署之前，这些干预措施必须持续实施，因为否则，许多易感个体仍有感染风险。我们使用一个简单的分析模型来探究低水平感染与疫苗接种相结合如何决定实现群体免疫的轨迹。了解这种情况下病毒生命周期生物学特性的影响至关重要。我们通过对有效繁殖数[公式：见原文]维持在1的情况进行建模，对这一过程进行了简单描述。由于传播阻断免疫的强度和持续时间所带来的额外复杂性尚不清楚，我们利用我们的框架来探究这些不确定性的影响。通过直观的分析关系，我们探究了疫苗接种率和缓解措施的必要幅度如何关键地取决于自然免疫和疫苗免疫的持续时间。我们还表明，我们的框架可以涵盖由于在强有力的缓解措施之前的流行动态所导致的季节性或既往免疫情况。综上所述，我们简单的概念模型说明了个体免疫和疫苗免疫对群体免疫的重要性，并且对针对SARS-CoV-2免疫的个体进行量化至关重要。
