SARS-CoV-2 aerosol transmission in schools: the effectiveness of different interventions

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Abstract

BACKGROUND: Indoor aerosol transmission of SARS-CoV-2 has been widely recognised, especially in schools where children remain in closed indoor spaces and largely unvaccinated. Measures such as strategic natural ventilation and high efficiency particulate air (HEPA) filtration remain poorly implemented and mask mandates are often progressively lifted as vaccination rollout is enhanced. METHODS: We adapted a previously developed aerosol transmission model to study the effect of interventions (natural ventilation, face masks, HEPA filtration and their combinations) on the concentration of virus particles in a classroom of 160 m3 containing one infectious individual. The cumulative dose of viruses absorbed by exposed occupants was calculated. RESULTS: In the absence of interventions, the cumulative dose absorbed was 1.5 times higher in winter than in spring/summer, increasing chances of indoor airborne transmission in winter. However, natural ventilation was more effective in winter, leading to up to a 20-fold decrease in cumulative dose when six windows were fully open at all times. In winter, partly opening two windows all day or fully opening six windows at the end of each class was effective as well (2.7- to 3-fold decrease). In summer, good ventilation levels could be achieved through the opening of windows all day long (2- to 7-fold decrease depending on the number of windows open). Opening windows only during yard and lunch breaks had minimal effect (≤1.5-fold decrease). One HEPA filter was as effective as two windows partly open all day in winter (3-fold decrease) whereas two filters were more effective (5-fold decrease). Surgical face masks were very effective independently of the season (8-fold decrease). Combined interventions (i.e., natural ventilation, masks, and HEPA filtration) were the most effective (≥25-fold decrease) and remained highly effective in the presence of a super-spreader. INTERPRETATION: Natural ventilation, face masks, and HEPA filtration are effective interventions to reduce SARS-CoV-2 aerosol transmission. These measures should be combined and complemented by additional interventions (e.g., physical distancing, hygiene, testing, contact tracing and vaccination) to maximise benefit.

Article activity feed

  1. Brian Pavilonis

    Review 3: "SARS-CoV-2 Aerosol Transmission in Schools: The Effectiveness of Different Interventions"

    Reviewers find this a straightforward modelling study, though ask for clarification on some assumptions and emphasize that the results may apply only to naturally-ventilated classrooms.

  2. Richard M. Lynch, Ph.D.

    Review 2: "SARS-CoV-2 Aerosol Transmission in Schools: The Effectiveness of Different Interventions"

    Reviewers find this a straightforward modelling study, though ask for clarification on some assumptions and emphasize that the results may apply only to naturally-ventilated classrooms.

  3. Jacob Bueno de Mesquita

    Review 1: "SARS-CoV-2 Aerosol Transmission in Schools: The Effectiveness of Different Interventions"

    Reviewers find this a straightforward modelling study, though ask for clarification on some assumptions and emphasize that the results may apply only to naturally-ventilated classrooms.

  4. Strength of evidence

    Reviewers: Jacob Bueno de Mesquita, Ph.D (UC Berkeley) | 📗📗📗📗◻️
    Richard M. Lynch, Ph.D (Preferred Management Corporation) | 📗📗📗📗◻️
    Brian Pavilonis (CUNY School of Public Health) | 📒📒📒 ◻️◻️

  5. SciScore for 10.1101/2021.08.17.21262169: (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

    No key resources detected.


    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:
    One important limitation of our model comes from the lack of consensus regarding the infectious dose. Hence, we cannot predict, on a quantitative level, what measures are sufficient to keep the occupants of the room safe. Nonetheless, reducing the number of inhaled virions will result in an exponential reduction in the probability of …