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Mask-Wearing Reduces COVID-19 Transmission, Study Finds

Mask-wearing is associated with a significant reduction in COVID-19 transmission and factors other than mandates contributed to the global uptake of mask-wearing in 2020, new research has found.

The study led by academics at the Universities of Bristol, Oxford and Copenhagen is  published on the preprint server medRxiv.

Mask-wearing is an important barrier to COVID-19 transmission based on experimental studies, such as: droplets or aerosols generated by someone talking with or without a mask, and in animal models, but it is harder to find this effect in epidemiological data.

The research team analysed the effect of mask-wearing on COVID-19 transmission using the largest survey of mask-wearing (n=20 million) and obtained estimates from 92 regions across six continents. The researchers’ analysis goes further than past work due to the quality of wearing data − 100 times the sample size, with random sampling − the geographical scope, the sophistication of the infection model, and the validation of results.

Using a statistical technique known as hierarchical Bayesian modelling, the researchers estimated the effect of both mask-wearing and mask mandates on transmission by linking wearing levels (or mandates) to reported cases in each region, adjusting for mobility and non-pharmaceutical interventions.

The study found mask-wearing reduces COVID-19 transmission by around 25 per cent if everyone wears them.  Previous work has looked for R to decrease at the time of a government mask mandate, but the research found actual mask-wearing rises in anticipation, before the mandate, and then after the mandate compliance increases slowly as people get used to mask-wearing.  The research suggests that transmission is strongly predicted by mask-wearing, but not by mask mandates.

Dr Laurence Aitchison, Lecturer in Machine Learning and Computational Neuroscience in the Department of Computer Science at the University of Bristol and a senior author on the paper, said: “At a time where mask-wearing is decreasing and mask mandates are being lifted, our research confirms that masks do indeed have a strong impact on COVID-19 transmission in the population and remain an important measure in our response against the disease.”

The research team will continue to adjust their model to capture the effect of new variants on mask-wearing, together with the type of masks worn.


‘Mass mask-wearing notably reduces COVID-19 transmission

’ by Gavin Leech, Charlie Rogers-Smith et al in medRxiv

Please note this is a preprint, it is a preliminary piece of research that has not yet been through peer review and has not been published in a scientific journal – so this is early data.

Bristol UNCOVER Group In response to the COVID-19 crisis, researchers at the University of Bristol formed the Bristol COVID Emergency Research Group (UNCOVER) to pool resources, capacities and research efforts to combat this infection.

Bristol UNCOVER includes clinicians, immunologists, virologists, synthetic biologists, aerosol scientists, epidemiologists and mathematical modellers and has links to behavioural and social scientists, ethicists and lawyers.

Follow Bristol UNCOVER on Twitter at: twitter.com/BristolUncover

For more information about the University of Bristol’s coronavirus (COVID-19) research priorities visit: http://www.bristol.ac.uk/research/impact/coronavirus/research-priorities/

COVID-19 research outputs A full list of University of Bristol research outputs relating to the COVID-19 pandemic is available online.

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