Modelling the potential impact of mask use in schools and society on COVID-19 control in the UK

Abstract

As the UK reopened after the first wave of the COVID-19 epidemic, crucial questions emerged around the role for ongoing interventions, including test-trace-isolate (TTI) strategies and mandatory masks. Here we assess the importance of masks in secondary schools by evaluating their impact over September 1-October 23, 2020. We show that, assuming TTI levels from August 2020 and no fundamental changes in the virus's transmissibility, adoption of masks in secondary schools would have reduced the predicted size of a second wave, but preventing it would have required 68% or 46% of those with symptoms to seek testing (assuming masks' effective coverage 15% or 30% respectively). With masks in community settings but not secondary schools, the required testing rates increase to 76% and 57%.

Figure 1

(A) Schematic of the model component showing the modelled effect from using face coverings. (B) Illustration of the different levels modelled in Covasim. (C) Results of the model calibration showing the matching of the model projected cumulative COVID-19 cases and cumulative deaths associated with COVID-19 with the data from https://coronavirus.data.gov.uk. Data is shown in thick blue/black lines, medians across twelve simulations are indicated by thin blue/blue lines and 10% and 90% quantiles by blue/grey shading.

Figure 2

Heatmaps of cumulative infections for different trace (x-axis) and test (y-axis) levels across the scenario of mask wearing in parts of community with and without schools masks’ wear. Higher cumulative infections are shown in darker shades of red, while lower values are lighter colours. The region of a light orange colour where cumulative infections remain below 500,000, represents a region within where the second wave of COVID-19 after September 2020 is avoided with combinations of adequate test-trace and mask usage.

Figure 3

Model scenarios of potential second COVID-19 epidemic wave in the UK during 2020 under different policies of mask wearing and effective coverage, assuming a testing level of 24% and school/workplace tracing levels of 50%. Medians across 30 simulations are indicated by solid red lines and 10% and 90% quantiles by red shading. The resurgence of COVID-19 after September 2020 is controlled and second wave avoided with combinations of adequate test-trace and mask usage if the median number of daily infections remains below 20,000 over the simulation period.

Figure 4

Model scenarios of potential second COVID-19 epidemic wave in the UK during 2020 under different policies of mask wearing and effective coverage for testing and tracing levels where future the resurgence of COVID-19 is prevented. Medians across 30 simulations are indicated by solid red lines and 10% and 90% quantiles by red shading. The resurgence of COVID-19 after September 2020 is controlled and second wave avoided with combinations of adequate test-trace and mask usage if the median number of daily infections remains below 20,000 over the simulation period.