Modelling the impact of the mandatory use of face coverings on public transport and in retail outlets in the UK on COVID-19-related infections, hospital admissions and mortality

Abstract

Introduction
The rapid spread of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV26 2/)(COVID-19) virus resulted in governments around the world instigating a range of measures, including mandating the wearing of face coverings on public transport/in retail outlets.

Methods
We developed a sequential assessment of the risk reduction provided by face coverings using a step-by-step approach. The United Kingdom Office of National Statistics (ONS) Population Survey data was utilised to determine the baseline total number of community-derived infections. These were linked to reported hospital admissions/hospital deaths to create case admission risk ratio and admission-related fatality rate. We evaluated published evidence to establish an infection risk reduction for face coverings. We calculated an Infection Risk Score (IRS) for a number of common activities and related it to the effectiveness of reducing infection and its consequences, with a face covering, and evaluated their effect when applied to different infection rates over 3 months from 24th 36 July 2020, when face coverings were made compulsory in England on public transport/retail outlets.

Results
We show that only 7.3% of all community-based infection risk is associated with public transport/retail outlets. In the week of 24th 40 July, The reported weekly community infection rate was 29,400 new cases at the start (24th July). The rate of growth in hospital admissions and deaths for England was around -15%/week, suggesting the infection rate, R, in the most vulnerable populations was just above 0.8. In this situation, average infections over the evaluated 13 week follow-up period, would be 9,517/week with face covering of 40% effectiveness, thus reducing average infections by 844/week, hospital admissions by 8/week and deaths by 0.6/week; a fall of 9% over the period total. If, however, the R-value rises to 1.0, then average community infections would stay at 29,400/week and mandatory face coverings could reduce average weekly infections by 3,930, hospital admissions by 36 and deaths by 2.9/week; a 13% reduction. These reductions should be seen in the context that there was an average of 102,000/week all-cause hospital emergency admissions in England in June and 8,900 total reported deaths in the week ending 7th August 2020.

Conclusion
We have illustrated that the policy on mandatory use of face coverings in retail outlets/on public transport may have been very well followed, but may be of limited value in reducing hospital admissions and deaths, at least at the time that it was introduced, unless infections begin to rise faster than currently seen. The impact appears small compared to all other sources of risk, thereby raising questions regarding the effectiveness of the policy.