Measuring the scientific effectiveness of contact tracing: Evidence from a natural experiment

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 vaccination rates increase and spread COVID-19 slows, which makes individual cases possible. However, because randomized experiments on contact are infeasible, causal evidence about effectiveness is missing. This shortage alarming governments around world invest in large-scale systems, frequently facing a lack cooperation from population. Exploiting natural experiment, we provide may be even more effective than indicated by correlational research. Our findings inform current future health responses to infectious diseases.