Modeling the Comparative Impact of Individual Quarantine vs. Active Monitoring of Contacts for the Mitigation of COVID-19

Corey M Peak; Rebecca Kahn; Yonatan H Grad; Lauren M Childs; Ruoran Li; Marc Lipsitch; Caroline O Buckee

The fraction of contacts traced is a particularly influential consideration. As the probability of tracing an infected contact decreases, more cases are able to transmit the infection without isolation and therefore, there is a linear increase in the average or across the R IQ R AM population ( Figure 5 ). Even with other operational parameters reflecting a high feasibility setting, at least three-quarters of contacts need to be traced and quarantined to reduce in the R e < 1 population in the absence of other interventions. For those individuals who are traced and placed under active monitoring or individual quarantine, however, the impact of the interventions at reducing onward transmission by that person remains effective. Even if only a small proportion of infected contacts are traced, therefore, the transmission chains those contacts could create can be prevented. The extent to which it is worth investing in imperfect contact tracing will depend on the rate of epidemic growth, which affects feasibility, and the other mix of interventions being considered.