Determining the optimal strategy for reopening schools, the impact of test and trace interventions, and the risk of occurrence of a second COVID-19 epidemic wave in the UK: a modelling study
Determining the optimal strategy for reopening schools, the impact of test and trace interventions, and the risk of occurrence of a second COVID-19 epidemic wave in the UK: a modelling study
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DOI：
10.1016/s2352-4642(20)30250-9
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发表时间：
2020-11-01
影响因子：
36.4
通讯作者：
Bonell, Chris
中科院分区：
文献类型：
--
作者：
Panovska-Griffiths, Jasrnino;Kerr, Cliff C.;Bonell, Chris
背景随着英国开始放松减缓严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染传播的封锁措施，评估任何政策变化的影响非常重要，包括学校重新开放和更广泛地放松社交距离措施。我们的目标是使用基于个人的模型来预测从 2020 年 9 月起向英国所有学生重新开放学校的两种可能策略的影响，并结合关于放松物理距离措施和扩大测试规模的不同假设。方法在这项建模研究中，我们使用了 Covasim，这是一种基于个人的随机 SARS-CoV-2 传播模型，已根据英国疫情进行了校准。该模型描述了个人的联系网络，分为家庭、学校、工作场所和社区层，并使用来自英国的人口和流行病学数据。我们模拟了六种不同的场景，代表两种学校重新开放策略（全日制和非全日制轮班制，50% 的学生隔周上学）和三种测试场景（68% 的接触者追踪，不扩大测试规模，68% 的接触者追踪，经过充分的测试以避免第二波 COVID-19，以及 40% 的接触者追踪，经过充分的测试以避免第二波 COVID-19）。我们估计了不同策略下的新增感染人数、病例数和死亡人数，以及有效繁殖数（R）。在考虑随机模拟不确定性的敏感性分析中，我们还模拟了 20 岁以下儿童和年轻人相对于较大年龄（20 岁及以上）的 50% 的传染性。结果：随着检测水平的提高（59% 至 87% 的有症状人群在活跃 SARS-CoV-2 感染期间的某个时间点进行了检测，具体取决于具体情况），以及有效的接触者追踪和隔离，可能会防止疫情反弹。假设可以追踪到 68% 的接触者，我们估计，如果学校在 9 月份全日制返校，则需要对 75% 有症状感染者进行检测，并隔离阳性病例；如果采用非全日制轮班制度，则需要隔离 65% 的接触者。如果只能追踪 40% 的接触者，这些数字将分别增加到 87% 和 75%。然而，如果没有这些水平的检测和接触者追踪，学校重新开放以及逐步放松封锁措施可能会引发第二波浪潮，如果学校在 9 月份全日制开放，则第二波浪潮将在 2020 年 12 月达到顶峰；如果采用非全日制轮值制度，则在 2021 年 2 月达到顶峰。无论哪种情况，第二波都会导致 R 上升到 1 以上，从而导致第二波感染规模是原始 COVID-19 波的 2.0-2.3 倍。当儿童和年轻人的传染性从老年人的 100% 到 50% 不等时，我们仍然发现需要采取全面有效的检测-追踪-隔离策略来避免第二波 COVID-19 浪潮。 解读 为了防止第二波 COVID-19 浪潮，在英国放宽身体距离（包括重新开放学校）的同时，必须对有症状的个体进行大规模、全人口的检测并有效追踪其接触者，然后隔离确诊个体。
Background As lockdown measures to slow the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection begin to ease in the UK, it is important to assess the impact of any changes in policy, including school reopening and broader relaxation of physical distancing measures. We aimed to use an individual-based model to predict the impact of two possible strategies for reopening schools to all students in the UK from September, 2020, in combination with different assumptions about relaxation of physical distancing measures and the scale-up of testing.Methods In this modelling study, we used Covasim, a stochastic individual-based model for transmission of SARS-CoV-2, calibrated to the UK epidemic. The model describes individuals' contact networks stratified into household, school, workplace, and community layers, and uses demographic and epidemiological data from the UK. We simulated six different scenarios, representing the combination of two school reopening strategies (full time and a part-time rota system with 50% of students attending school on alternate weeks) and three testing scenarios (68% contact tracing with no scale-up in testing, 68% contact tracing with sufficient testing to avoid a second COVID-19 wave, and 40% contact tracing with sufficient testing to avoid a second COVID-19 wave). We estimated the number of new infections, cases, and deaths, as well as the effective reproduction number (R) under different strategies. In a sensitivity analysis to account for uncertainties within the stochastic simulation, we also simulated infectiousness of children and young adults aged younger than 20 years at 50% relative to older ages (20 years and older).Findings With increased levels of testing (between 59% and 87% of symptomatic people tested at some point during an active SARS-CoV-2 infection, depending on the scenario), and effective contact tracing and isolation, an epidemic rebound might be prevented. Assuming 68% of contacts could be traced, we estimate that 75% of individuals with symptomatic infection would need to be tested and positive cases isolated if schools return full-time in September, or 65% if a part-time rota system were used. If only 40% of contacts could be traced, these figures would increase to 87% and 75%, respectively. However, without these levels of testing and contact tracing, reopening of schools together with gradual relaxing of the lockdown measures are likely to induce a second wave that would peak in December, 2020, if schools open full-time in September, and in February, 2021, if a part-time rota system were adopted. In either case, the second wave would result in R rising above 1 and a resulting second wave of infections 2.0-2.3 times the size of the original COVID-19 wave. When infectiousness of children and young adults was varied from 100% to 50% of that of older ages, we still found that a comprehensive and effective test-trace-isolate strategy would be required to avoid a second COVID-19 wave.Interpretation To prevent a second COVID-19 wave, relaxation of physical distancing, including reopening of schools, in the UK must be accompanied by large-scale, population-wide testing of symptomatic individuals and effective tracing of their contacts, followed by isolation of diagnosed individuals.