Which policies most effectively reduce SARS-CoV-2 transmission in schools?

  1. Anna Bershteyn
  2. Hae-Young Kim
  3. Jessica McGillen
  4. R. Scott Braithwaite

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Abstract

Introduction

New York City (NYC) has the largest public school system in the United States (US). During the SARS-CoV-2 pandemic, NYC was the first major US city to open schools for in-person learning in the 2020-2021 academic year. Several policies were implemented to reduce the risk of in-school transmission, including infection control measures (facemasks, physical distancing, enhanced indoor ventilation, cohorting of small groups, and hand hygiene), option of all-remote instruction, alternative options for how class schedules would rotate in-person and remote instruction, daily symptom screening, and testing 10-20% of students and staff weekly or monthly depending on local case rates. We sought to determine which of these policies had the greatest impact on reducing the risk of in-school transmission.

Methods

We evaluated the impact of each policy by referring to global benchmarks for the secondary attack rate (SAR) of SARS-CoV-2 in school settings and by simulating the potential for transmission in NYC’s rotating cohort schedules, in which teachers could act as “bridges” across rotating cohorts. We estimated the impact of (1) infection control measures, (2) providing an option of all-remote instruction, (3) choice of class scheduling for in-person learners, (4) daily symptom screening, (5) testing to curtail transmission, and (6) testing to identify school outbreaks. Each policy was assessed independently of other policies, with the exception of symptom screening and random testing, which were assessed both independently and jointly.

Results

Among the policies analyzed, the greatest transmission reduction was associated with the infection control measures, followed by small class cohorts with an option for all-remote instruction, symptom screening, and finally randomly testing 10-20% of school attendees. Assuming adult staff are the primary source of within-school SARS-CoV-2 transmission, weekly testing of staff could be at least as effective as symptom screening, and potentially more so if testing days occur in the beginning of the workweek with results available by the following day. A combination of daily symptom screening and testing on the first workday of each week could reduce transmission by 70%.

Conclusions

Adherence to infection control is the highest priority for safe school re-opening. Further transmission reduction can be achieved through small rotating class cohorts with an option for remote learning, widespread testing at the beginning of the work week, and daily symptom screening and self-isolation. Randomly testing 10-20% of attendees weekly or monthly does not meaningfully curtail transmission and may not detect outbreaks before they have spread beyond a handful of individuals. School systems considering re-opening during the SARS-CoV-2 pandemic or similarly virulent respiratory disease outbreaks should consider these relative impacts when setting policy priorities.

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  1. ScreenIT

    SciScore for 10.1101/2020.11.24.20237305: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Antibodies
    SentencesResources
    In the study, 0.6% of attendees tested positive for SARS-CoV-2 antibodies with no clusters exceeding 4 individuals.
    SARS-CoV-2
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    A limitation of this policy is that policy-makers cannot control and may struggle to anticipate the fraction of students who will opt for fully-remote instruction. The specific rotation schedule had little impact on the risk of transmission, even if a teacher were to become infected and act as a “bridge” across cohorts. There was greater transmission risk in rotation schedules that involved larger cohorts with more days of in-person attendance per student, but these effects were modest compared to the large impact of infection control and providing an option of fully-remote learning. These findings suggest that schools should select the rotation schedule most conducive to their education mission, while focusing on infection control as a primary means of transmission prevention. Testing and symptom screening may have a moderate contribution to reducing transmission even under optimistic assumptions. We found that daily symptom screening could reduce transmission by one-third to two-fifths, while NYC’s strategy of testing 10-20% of school attendees had little direct effect on transmission reduction, nor could these testing rates reliably detect outbreaks before they spread beyond a handful of individuals. At these rates of in-school testing, detection of smaller outbreaks depends upon the initiative of students and staff to seek outside testing at health facilities and test centers. In NYC, testing was free and unrestricted throughout the fall of 2020; other school districts sh...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  2. Version published to 10.1101/2020.11.24.20237305v1 on medRxiv