The epidemiological impact of the NHS COVID-19 app
The epidemiological impact of the NHS COVID-19 app
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DOI：
10.1038/s41586-021-03606-z
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发表时间：
2021-05-12
期刊：
影响因子：
64.8
通讯作者：
Fraser, Christophe
中科院分区：
文献类型：
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作者：
Wymant, Chris;Ferretti, Luca;Fraser, Christophe
在2019冠状病毒病大流行期间，出现了数字接触者追踪，以帮助防止疾病传播。手机应用程序记录了应用程序用户之间的接近事件，当用户的新冠病毒检测呈阳性时，可以立即通知他们最近的联系人。理论证据支持这种新的公共卫生干预（1-6），但其流行病学影响仍不确定(7)。在这里，我们调查了国家卫生服务（NHS） COVID-19应用程序对英格兰和威尔士的影响，从2020年9月24日推出到2020年12月底。大约有1650万用户（占总人口的28%）定期使用它，并发送了大约170万份暴露通知：每个索引病例有4.2人同意追踪接触者。我们估计，应用程序通知的随后出现症状并检测呈阳性的个体比例（二次发作率（SAR））为6%，与手动追踪密切接触者的SAR相似。我们使用两种互补的方法估计了该应用程序避免的病例数量：基于通知和SAR的建模估计为284,000（中心95%敏感性分析范围为108,000-450,000），而匹配的邻近地方当局的统计比较估计为594,000（95%置信区间为317,000-914,000）。每一个同意通知其接触者的病例大约避免了一个病例。我们估计，应用使用率每增加一个百分点，案例数量就会减少0.8%（基于模型）或2.3%（基于统计分析）。这些发现支持在等待疫苗完全保护的人群中继续开发和部署此类应用程序。
The COVID-19 pandemic has seen the emergence of digital contact tracing to help to prevent the spread of the disease. A mobile phone app records proximity events between app users, and when a user tests positive for COVID-19, their recent contacts can be notified instantly. Theoretical evidence has supported this new public health intervention(1-6), but its epidemiological impact has remained uncertain(7). Here we investigate the impact of the National Health Service (NHS) COVID-19 app for England and Wales, from its launch on 24 September 2020 to the end of December 2020. It was used regularly by approximately 16.5 million users (28% of the total population), and sent approximately 1.7 million exposure notifications: 4.2 per index case consenting to contact tracing. We estimated that the fraction of individuals notified by the app who subsequently showed symptoms and tested positive (the secondary attack rate (SAR)) was 6%, similar to the SAR for manually traced close contacts. We estimated the number of cases averted by the app using two complementary approaches: modelling based on the notifications and SAR gave an estimate of 284,000 (central 95% range of sensitivity analyses 108,000-450,000), and statistical comparison of matched neighbouring local authorities gave an estimate of 594,000 (95% confidence interval 317,000-914,000). Approximately one case was averted for each case consenting to notification of their contacts. We estimated that for every percentage point increase in app uptake, the number of cases could be reduced by 0.8% (using modelling) or 2.3% (using statistical analysis). These findings support the continued development and deployment of such apps in populations that are awaiting full protection from vaccines.