Masks in Reducing the Spread of Infectious Disease

COMMENTARY: Masks-for-all for COVID-19 not based on sound data

Lisa M Brosseau ScD; Margaret Sietsema, PhD

Sweeping mask recommendations—as many have proposed—will not reduce SARS-CoV-2 transmission, as evidenced by the widespread practice of wearing such masks in Hubei province, China, before and during its mass COVID-19 transmission experience earlier this year. Our review of relevant studies indicates that cloth masks will be ineffective at preventing SARS-CoV-2 transmission, whether worn as source control or as PPE. 

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Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers

The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use. The data were compatible with lesser degrees of self-protection.

“However, WHO acknowledges that we lack evidence that wearing a mask protects healthy persons from SARS-CoV-2 (prevention).”

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A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

C Raina MacIntyre; Holly Seale; Tham Chi Dung; Nguyen Tran Hien; Phan Thi Nga; Abrar Ahmad Chughtai;, Bayzidur Rahman; Dominic E Dwyer;, Quanyi Wang

This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.

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Surgical mask to prevent influenza transmission in households: a cluster randomized trial

Laetitia Canini; Laurent Andréoletti; Pascal Ferrari; Romina D'Angelo; Thierry Blanchon; Magali Lemaitre; Laurent Filleul; Jean-Pierre Ferry; Michel Desmaizieres; Serge Smadja; Alain-Jacques Valleron; Fabrice Carrat

In various sensitivity analyses, we did not identify any trend in the results suggesting effectiveness of facemasks.

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Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?

Anna Davies; Katy-Anne Thompson; Karthika Giri; Georged Kafatos; Jimmy Walker; Allan Bennett

Homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals.

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Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial

Joshua L Jacobs; Sachiko Ohde; Osamu Takahashi; Yasuharu Tokuda; Fumio Omata; Tsuguya Fukui

Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds.

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Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis

Jeffrey D. Smith MSc; Colin C. MacDougall MSc; Jennie Johnstone MD PhD; Ray A. Copes MD; Brian Schwartz MD; Gary E. Garber MD

Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.

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A replaceable, more efficient filter for N95 masks

American Chemical Society

N95 masks provide the “highest level of protection,” but this new filter has a smaller pore size, “potentially blocking more virus particles.”

[But…surgical masks work as well as N95 for influenza transmission.]

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