The role of face coverings in mitigating the transmission of SARS-CoV-2: An overview of evidence.


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The role of face coverings in mitigating the transmission of SARS-CoV-2: An overview of evidence.
Radford Gina, Cattini pat, Cevic Muge, Evans Cariad, Houlihan Catherine, Jerwood Susie, Lipman Marc, Newsholme William, Noakes Catherine, Paszkiewicz Peter, Poller Jenny, Szalajda Jon, Vernez David, Wilson Jennie, Wilson Peter, Winchester Stephen
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UK Health Security Agency
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rapport gouvernemental
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This paper draws on review-level evidence (searches up to 28 April 2021) to consider the potential effectiveness of face coverings in mitigating transmission of SARS-CoV-2. It includes evidence examining:
• the role of airborne transmission in relation to SARS-CoV-2
• the transmissibility of new SARS-CoV-2 variants
• the effectiveness of face coverings, including efficacy of different types of face coverings and factors that may impact on this
Current evidence on the potential for airborne transmission of SARS-CoV-2 is heterogeneous and mainly based on environmental sampling studies, modelling studies and outbreak investigations. While sampling studies suggest that SARS-CoV-2 can be detected in the environment, they usually do not provide evidence on infectiousness of the aerosols. Evidence from outbreak investigations suggests that long distance airborne transmission can occur and when it happens, it is usually in poorly ventilated indoor settings where the potential primary and secondary cases have stayed for extended durations of time. Other factors such as air flow or singing might also be contributing factors for long distance airborne transmission. Airborne transmission can also occur in healthcare settings, although it might predominantly happen during aerosol generating procedures.
Evidence on the transmissibility of new variants of concern is still in its early stages and based on a small number of low-quality reviews. The available evidence suggests an increased transmissibility for Alpha variant (B.1.1.7), although the magnitude of reported increase varies by geographic region, modelling approach, relative transmissibility of concurrent circulating strains and current control measures in place. The evidence available for Beta (B.1.351) and Gamma (P.1) variants is more limited but does also suggest an increased transmissibility (Delta/B.1617.2 variant was not considered). The biological mechanism of the increase in transmissibility is not yet clear though for Alpha variant (B.1.1.7) the most likely explanations are increased viral load and lower average infectious dose required to start infection.
The current evidence on face coverings suggests that all types of face coverings are, to some extent, effective in reducing transmission of SARS-CoV-2 in both healthcare and community settings. N95 respirators are likely to be the most effective, followed by surgical masks, and then non-medical masks, although optimised non-medical masks made of 2 or 3 layers might have similar filtration efficiency to surgical masks. The evidence specific to coronavirus (COVID-19) is still limited and does not allow for firm conclusions to be drawn for specific settings and type of face coverings. Wider evidence from other respiratory viruses suggests that, in healthcare settings, N95 respirators might be more effective than surgical masks in reducing infection risk.
Evidence mainly based on laboratory studies suggests that face coverings should be well-fitted to increase effectiveness.
No evidence on the effectiveness of face coverings against specific variants of SARS-CoV-2 was identified.
More research is needed to fully understand the contribution of airborne transmission to the COVID-19 pandemic and factors that may influence this. More robust research from well-designed intervention studies is also needed to better understand the effectiveness of different types of face coverings in mitigating the risk of different modes of transmission across settings. Finally, more research is needed to improve knowledge on how face coverings are used by subgroups of the population across settings and how this might impact on their effectiveness.
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21/10/2021 17:47
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22/04/2022 13:48
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