Alliance for Pandemic Preparedness

November 9, 2020

Effectiveness of Contact Tracing and Quarantine on Reducing COVID-19 Transmission: A Retrospective Cohort Study

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A cohort study among COVID-19 patients in Portugal (n=551) from March 1 to April 30, 2020 found no significant difference in the attack rate from index cases between patients who received contact tracing, isolated and had close contacts who were quarantined and those who did not (12%, 95% CI 7–19% vs. 9%, 95% CI 8–11%, respectively). Patients who were traced had a shorter time between symptom onset and laboratory diagnosis (median 3 vs. 5 days, p=0.004) and fewer close contacts (median: 0 vs. 2 per index case, p<0.001) compared to patients who were not traced. 

Malheiro et al. (Sept 29, 2020). Effectiveness of Contact Tracing and Quarantine on Reducing COVID-19 Transmission: A Retrospective Cohort Study. Public Health. https://doi.org/10.1016/j.puhe.2020.09.012