Table 1 Policy summary

Background

Understanding how isolation, contact tracing and other non-pharmaceutical interventions can be combined effectively and efficiently is crucial to maintaining COVID-19 control. We developed an epidemic model that simulates COVID-19 outbreaks in a real-world network and assessed the impact of a range of testing, isolation, quarantine and contact tracing strategies for controlling new local outbreaks.

Main findings and limitations

We found that tracing and quarantining contacts of contacts was the most effective simulated measure for controlling local COVID-19 outbreaks but required large numbers of individuals to be quarantined. This strategy is similar to introducing a local lockdown. Testing and releasing quarantined individuals reduced the numbers quarantined but also reduced the effectiveness of control measures. Combining physical distancing with contact tracing resulted in reduced outbreak size, with fewer individuals required to quarantine. A major limitation of this study is that it is based on pre-COVID-19 social network data from a sample of individuals from a single small town; more data are needed to fully understand potential outbreak dynamics in other settings.

Policy implications

Our findings suggest that effective contact tracing measures could require large numbers of people in a community to be quarantined, with individual-level tracing resulting in outcomes equivalent to broad local lockdowns. Targeted tracing and quarantine strategies might be less disruptive overall when combined with other control measures such as moderate physical distancing.