期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：33
DOI：10.1073/pnas.2100814118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Contact tracing constitutes the backbone of nonpharmaceutical public interventions against COVID-19, as it did with previous pandemics. Experts argue that its importance rises again as vaccination rates increase and the spread of COVID-19 slows, which makes tracing of individual cases possible. However, because randomized experiments on contact tracing are infeasible, causal evidence about its effectiveness is missing. This shortage of evidence is alarming as governments around the world invest in large-scale contact tracing systems, frequently facing a lack of cooperation from the population. Exploiting a large-scale natural experiment, we provide evidence that contact tracing may be even more effective than indicated by previous correlational research. Our findings inform current and future public health responses to the spread of infectious diseases.
Contact tracing has for decades been a cornerstone of the public health approach to epidemics, including Ebola, severe acute respiratory syndrome, and now COVID-19. It has not yet been possible, however, to causally assess the method’s effectiveness using a randomized controlled trial of the sort familiar throughout other areas of science. This study provides evidence that comes close to that ideal. It exploits a large-scale natural experiment that occurred by accident in England in late September 2020. Because of a coding error involving spreadsheet data used by the health authorities, a total of 15,841 COVID-19 cases (around 20% of all cases) failed to have timely contact tracing. By chance, some areas of England were much more severely affected than others. This study finds that the random breakdown of contact tracing led to more illness and death. Conservative causal estimates imply that, relative to cases that were initially missed by the contact tracing system, cases subject to proper contact tracing were associated with a reduction in subsequent new infections of 63% and a reduction insubsequent COVID-19–related deaths of 66% across the 6 wk following the data glitch.
