Abstract
Optimal quarantine length for COVID-19 infection is unclear, in part owing to limited empirical data. To assess postquarantine transmission risk for various quarantine lengths and potential associations between quarantine strictness and transmission risk. Retrospective cohort study in 4 US universities from September 2020 to February 2021, including 3641 university students and staff who were identified as close contacts to individuals who tested positive for SARS-CoV-2 infection. Individuals were tested throughout the 10 to 14-day quarantine, and follow-up testing continued at least weekly throughout the 2020-2021 academic year. Strict quarantine, including designated housing with a private room, private bathroom, and meal delivery, vs nonstrict, which potentially included interactions with household members. Dates of last known exposure, last negative test result, and first positive test result during quarantine. This study included 301 quarantined university students and staff who tested SARS-CoV-2-positive (of 3641 quarantined total). These 301 individuals had a median (IQR) age of 22.0 (20.0-25.0) years; 131 (43.5%) identified as female; and 20 (6.6%) were staff. Of the 287 self-reporting race and ethnicity according to university-defined classifications, 21 (7.3%) were African American or Black, 60 (20.9%) Asian, 17 (5.9%) Hispanic or Latinx, 174 (60.6%) White, and 15 (5.2%) other (including multiracial and/or multiethnic). Of the 301 participants, 40 (13.3%; 95% CI, 9.9%-17.6%) had negative test results and were asymptomatic on day 7 compared with 15 (4.9%; 95% CI, 3.0%-8.1%) and 4 (1.4%; 95% CI, 0.4%-3.5%) on days 10 and 14, respectively. Individuals in strict quarantine tested positive less frequently than those in nonstrict quarantine (10% vs 12%; P = .04). To maintain the 5% transmission risk used as the basis for US Centers for Disease Control and Prevention's 7-day test-based quarantine guidance, our data suggest that quarantine with quantitative polymerase chain reaction testing 1 day before intended release should be 10 days for nonstrict quarantine and 8 days for strict quarantine, as ongoing exposure during quarantine may be associated with the higher rate of positive test results following nonstrict quarantine.
Highlights
COVID-19, caused by SARS-CoV-2, has caused an unprecedented global public health crisis.[1]
To maintain the 5% transmission risk used as the basis for US Centers for Disease Control and Prevention’s 7-day test-based quarantine guidance, our data suggest that quarantine with quantitative polymerase chain reaction testing 1 day before intended release should be 10 days for nonstrict quarantine and 8 days for strict quarantine, as ongoing exposure during quarantine may be associated with the higher rate of positive test results following nonstrict quarantine
The US Centers for Disease Control and Prevention (CDC) initially recommended a 14-day quarantine period based on estimates of the upper bound of the SARS-CoV-2 incubation period.[2,3]
Summary
COVID-19, caused by SARS-CoV-2, has caused an unprecedented global public health crisis.[1]. Isolating infected individuals and identifying and quarantining their close contacts remain key strategies used to mitigate the spread of SARS-CoV-2. Quarantine length is a balance: a short quarantine brings increased risk of transmission from individuals who are infectious after release, while a long one may increase transmission risk by reducing compliance, stretching public health systems, and imposing additional economic and psychological hardship.[2]. The US Centers for Disease Control and Prevention (CDC) initially recommended a 14-day quarantine period based on estimates of the upper bound of the SARS-CoV-2 incubation period.[2,3]. While the CDC still recommends 14-day quarantine as the preferred option, in November 2020, to account for the costs of long quarantine, the organization identified 2 shorter quarantine options as acceptable alternatives for asymptomatic individuals based on local circumstances and resources. France instituted a 7-day quarantine and Belgium, Germany, and Spain adopted a 10-day period[4]; and, on the longer end, Chinese cities Beijing and Dalian adopted a 21-day quarantine period.[5]
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