The rapid growth rate of COVID-19 continues to threaten to overwhelm healthcare systems in multiple countries. In response, severely affected countries have had to impose a range of public health strategies achieved via nonpharmaceutical interventions. Broadly, these strategies have fallen into two categories: 1) “mitigation,” which aims to achieve herd immunity by allowing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus to spread through the population while mitigating disease burden, and 2) “suppression,” aiming to drastically reduce SARS-CoV-2 transmission rates and halt endogenous transmission in the target population. Using an age-structured transmission model, parameterized to simulate SARS-CoV-2 transmission in the United Kingdom, we assessed the long-term prospects of success using both of these approaches. We simulated a range of different nonpharmaceutical intervention scenarios incorporating social distancing applied to differing age groups. Our modeling confirmed that suppression of SARS-CoV-2 transmission is possible with plausible levels of social distancing over a period of months, consistent with observed trends. Notably, our modeling did not support achieving herd immunity as a practical objective, requiring an unlikely balancing of multiple poorly defined forces. Specifically, we found that 1) social distancing must initially reduce the transmission rate to within a narrow range, 2) to compensate for susceptible depletion, the extent of social distancing must be adaptive over time in a precise yet unfeasible way, and 3) social distancing must be maintained for an extended period to ensure the healthcare system is not overwhelmed.

COVID-19 的快速增长继续威胁着多个国家的医疗保健系统。作为应对措施，受影响严重的国家不得不实施一系列通过非药物干预措施实现的公共卫生战略。总体而言，这些策略分为两类：1）“缓解”，旨在通过允许严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）病毒在人群中传播，同时减轻疾病负担来实现群体免疫，以及2）“抑制”，旨在大幅降低 SARS-CoV-2 传播率并阻止目标人群的内源性传播。使用年龄结构的传播模型，参数化以模拟英国的 SARS-CoV-2 传播，我们评估了使用这两种方法的长期成功前景。我们模拟了一系列不同的非药物干预场景，其中包括适用于不同年龄组的社交距离。我们的模型证实，通过几个月内合理的社交距离水平，抑制 SARS-CoV-2 传播是可能的，这与观察到的趋势一致。值得注意的是，我们的模型并不支持将实现群体免疫作为一个实际目标，需要对多种定义不明确的力量进行不太可能的平衡。具体来说，我们发现：1）社交距离最初必须将传播率降低到一个狭窄的范围内，2）为了补偿易感损耗，社交距离的程度必须以精确但不可行的方式随着时间的推移而适应，3）社交距离必须长时间保持距离，以确保医疗保健系统不会不堪重负。