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New comprehensive review provides strong evidence that masks and respirators effectively reduce the transmission of respiratory infections like COVID-19, based on analysis of over 400 studies from multiple disciplines.

Four types of face masks arranged in a row on a flat surface: a dark cloth mask, a blue disposable surgical mask, a white KN95 mask, and a white N95 mask with a valve. The image accompanies a news story titled 'Comprehensive Review Confirms Mask Effectiveness Against Respiratory Infections, Urges Better Design and Policy Support' from the Department of Primary Care at the University of Oxford.

A comprehensive new review published in Clinical Microbiology Reviews provides strong evidence that masks and respirators are effective in reducing the transmission of respiratory infections like COVID-19. The review, conducted by an international team of 13 researchers, analysed over 400 studies from multiple disciplines, including epidemiology, public health, engineering, and social sciences.

'Our review confirms that masks work, with a clear dose-response effect,' said lead author Professor Trisha Greenhalgh from the Nuffield Department of Primary Care Health Sciences, University of Oxford. 'The more consistently and correctly you wear a mask, the better protected you are. Respirators, when worn continuously, provide even greater protection than ordinary masks.'

Masks, including cloth face coverings and disposable medical masks, help reduce the spread of respiratory droplets and aerosols. Respirators, such as N95 and FFP2 devices, are designed to filter out smaller airborne particles and fit more tightly to the face, providing a higher level of protection.

The team's novel contributions include re-analyses of key clinical trials and observational studies, as well as a synthesis of evidence from fields ranging from fluid dynamics to anthropology. This comprehensive approach allowed the researchers to not only assess the effectiveness of masks under experimental conditions, but also to explore the real-world factors that influence their use and impact.

While the review found no serious harms from mask-wearing, it did identify some challenges, such as discomfort, communication difficulties – for hearing-impaired people for example – and environmental waste. However, the authors frame these as opportunities for further research and improvement rather than fundamental flaws.

'We need to see these challenges as a call to action,' said co-author Dr Amanda Kvalsvig, an epidemiologist based at the University of Otago, who is herself deaf. 'By investing in better design, more inclusive policies, and clearer communication, we can optimise masks for real-world use and ensure that everyone can benefit from this powerful public health tool.'

The review also highlights the importance of clear, consistent public health messaging to support mask use and combat misinformation. While mask mandates can be effective, the authors emphasise the need for context-specific assessments that consider cultural factors and public acceptability.

'Masks are not just a technical intervention, but also a social and cultural one,' said co-author Professor Deborah Lupton from the University of New South Wales. 'To be effective, mask policies need to be grounded in an understanding of people's beliefs, behaviours, and real-world constraints.'

Looking forward, the researchers call for further studies to improve and optimise mask design, explore new technologies like nanotechnology, and develop more sustainable and inclusive solutions. They also emphasise the need for ongoing public engagement to bring about more evidence-based and constructive conversations around masks.

'This review shows that masks are a valuable tool in our pandemic response toolkit,' said Professor Greenhalgh. 'By continuing to build the evidence base, innovate in design, and engage the public, we can harness the full potential of masks to protect public health now and in future respiratory pandemics.'

Read the full article at:

Masks and respirators for prevention of respiratory infections: a state of the science review
Clinical Microbiology Reviews
DOI: 10.1128/cmr.00124-23


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