Background

In most countries, contacts of confirmed COVID-19 cases are asked to quarantine for 14 days after exposure to limit asymptomatic onward transmission. While theoretically effective, this policy places a substantial social and economic burden on both the individual and wider society, which might result in low adherence and reduced policy effectiveness. We aimed to assess the merit of testing contacts to avert onward transmission and to replace or reduce the length of quarantine for uninfected contacts.

Methods

We used an agent-based model to simulate the viral load dynamics of exposed contacts, and their potential for onward transmission in different quarantine and testing strategies. We compared the performance of quarantines of differing durations, testing with either PCR or lateral flow antigen (LFA) tests at the end of quarantine, and daily LFA testing without quarantine, against the current 14-day quarantine strategy. We also investigated the effect of contact tracing delays and adherence to both quarantine and self-isolation on the effectiveness of each strategy.

Findings

Assuming moderate levels of adherence to quarantine and self-isolation, self-isolation on symptom onset alone can prevent 37% (95% uncertainty interval [UI] 12–56) of onward transmission potential from secondary cases. 14 days of post-exposure quarantine reduces transmission by 59% (95% UI 28–79). Quarantine with release after a negative PCR test 7 days after exposure might avert a similar proportion (54%, 95% UI 31–81; risk ratio [RR] 0·94, 95% UI 0·62–1·24) to that of the 14-day quarantine period, as would quarantine with a negative LFA test 7 days after exposure (50%, 95% UI 28–77; RR 0·88, 0·66–1·11) or daily testing without quarantine for 5 days after tracing (50%, 95% UI 23–81; RR 0·88, 0·60–1·43) if all tests are returned negative. A stronger effect might be possible if individuals isolate more strictly after a positive test and if contacts can be notified faster.

Interpretation

Testing might allow for a substantial reduction in the length of, or replacement of, quarantine with a small excess in transmission risk. Decreasing test and trace delays and increasing adherence will further increase the effectiveness of these strategies. Further research is required to empirically evaluate the potential costs (increased transmission risk, false reassurance) and benefits (reduction in the burden of quarantine, increased adherence) of such strategies before adoption as policy.

Funding

National Institute for Health Research, UK Research and Innovation, Wellcome Trust, EU Horizon 2021, and the Bill & Melinda Gates Foundation.

中文翻译：

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SARS-CoV-2 接触者追踪中的检疫和检测策略：一项建模研究

背景

在大多数国家/地区，已确诊的 COVID-19 病例的接触者被要求在接触后隔离 14 天，以限制无症状的进一步传播。虽然在理论上是有效的，但这项政策给个人和更广泛的社会带来了沉重的社会和经济负担，这可能导致低遵守率和政策有效性降低。我们的目的是评估检测接触者以避免继续传播以及取代或缩短未感染接触者隔离时间的优点。

方法

我们使用基于代理的模型来模拟暴露接触者的病毒载量动态，以及它们在不同隔离和测试策略中继续传播的潜力。我们比较了不同持续时间的隔离、在隔离结束时使用 PCR 或侧向流动抗原 (LFA) 测试进行检测，以及没有隔离的每日 LFA 检测与当前 14 天隔离策略的性能。我们还调查了接触者追踪延迟以及坚持隔离和自我隔离对每种策略有效性的影响。

发现

假设中等程度地遵守检疫和自我隔离，仅在出现症状时进行自我隔离就可以防止 37%（95% 不确定区间 [UI] 12-56）的继发病例进一步传播的可能性。14 天的暴露后隔离可将传播减少 59%（95% UI 28–79）。暴露后 7 天 PCR 测试阴性后隔离释放可能会避免类似比例（54%，95% UI 31–81；风险比 [RR] 0·94，95% UI 0·62–1·24） 14 天隔离期的隔离期，以及在暴露后 7 天进行 LFA 测试阴性的隔离（50%、95% UI 28–77；RR 0·88、0·66–1·11）或无需隔离的每日测试追踪后 5 天（50%，95% UI 23–81；RR 0·88，0·60–1·43）如果所有测试返回阴性。

解释

测试可能会大大减少或取代隔离的时间，同时略微增加传播风险。减少测试和跟踪延迟并提高依从性将进一步提高这些策略的有效性。在作为政策采用之前，需要进一步研究以实证评估此类策略的潜在成本（增加传播风险、虚假保证）和收益（减少检疫负担、增加依从性）。

资金

国家卫生研究院、英国研究与创新、惠康基金会、欧盟地平线 2021 和比尔及梅琳达·盖茨基金会。