High Community Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Associated With Decreased Contact Tracing Effectiveness for Identifying Persons at Elevated Risk of Infection-Vermont.

Vermont contact tracing consistently identified people at risk for coronavirus disease 2019 (COVID-19). However, the prevalence ratio (PR) of COVID-19 among contacts compared with noncontacts when viral transmission was high (PR, 13.5 [95% confidence interval {CI}, 13.2-13.9]) was significantly less than when transmission was low (PR, 49.3 [95% CI, 43.2-56.3]).