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 ${\mathcal{R}}_{\mathrm{eff}}$ 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.

SARS-CoV-2是国际公共卫生突发事件；高传播性，发病率和死亡率会导致病毒压倒卫生系统。社会隔离，测试，跟踪和隔离策略的组合可以将每个感染个体的新感染数减少到1以下，从而促使病例数下降，但可能既具有挑战性又成本高。还必须维持这些干预措施，直到疫苗（或治疗剂）的开发和（现在可能）大规模部署为止，因为否则，许多易感人群仍然有感染的危险。我们使用一个简单的分析模型来探索低水平的感染，再加上疫苗接种，如何确定社区免疫的轨迹。在这种情况下，了解病毒生命周期生物学特性的影响非常重要。我们通过对有效繁殖数量的场景进行建模，来对此过程进行简单描述。${\mathcal{[R}}_{\mathrm{效}}$保持为1。由于尚未确定由传输阻止免疫的强度和持续时间带来的额外复杂性，因此我们使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，我们探索所需的疫苗接种率和缓解措施如何关键地取决于自然和疫苗免疫的持续时间。我们还表明，由于采取了强有力的缓解措施之前的流行病动态，我们的框架可以包括季节性或先前存在的免疫力。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社区免疫的重要性，而针对SARS-CoV-2免疫的个体的量化至关重要。