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COVID-19 news from Annals of Internal Medicine

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American College of Physicians

Below please find a summary and link(s) of new coronavirus-related content published today in Annals of Internal Medicine. The summary below is not intended to substitute for the full article as a source of information. A collection of coronavirus-related content is free to the public at

1. Review concludes universal mask use by lay persons reduces the spread of viral infections including SARS-CoV-2
Findings affirm policy promised by President-Elect Biden, who will ask Americans on Inauguration Day to wear masks for 100 days

A new narrative review of over 100 research articles concludes that masks and face coverings worn by members of the public reduce the spread of respiratory viral infections including SARS-CoV-2, the virus that causes Covid-19. The virus travels in the air in tiny droplets and particles, which are blocked to some extent even by 'imperfect' cloth face coverings. Wearing a face covering in a crowded indoor space reduces the chance that an infected person will pass the virus on to others. Even small reductions in the transmission rate can lead to large reductions in the number of people becoming infected over time.
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According to the authors from the University of Oxford, Institute for Advanced Studies, Vienna, Austria, and London School of Economics there is no evidence that masks and face coverings cause serious harm, though they can cause discomfort. There is also no evidence that wearing a mask leads to people stopping other protective behaviors, such as hand-washing. Resistance to mask-wearing is influenced by cultural norms and expectations; in some but not all cultures, the mask symbolizes the loss of autonomy and a threat to individual freedom. In such circumstances, mandated masking should be introduced only if the virus is spreading and cannot be controlled by other means.

The authors say this review is published at a critical time in the pandemic, as over 80 million people are known to have been infected with the virus and at least 1.75 million have so far died. Currently, over half a million people are becoming infected every day. While masks aren't a perfect barrier to the virus, the data strongly support wide-spread mask mandates, as observational studies suggest universal masking reduces transmission.

Media contacts: A PDF for this article is not yet available. Please click the link to read the full text. The lead corresponding author, Thomas Czypionka can be reached at

2. Update to 'living review' summarizes latest evidence on mask use among laypersons and health care workers
Researchers from Oregon Health & Sciences University published a fourth update to their living rapid review of evidence evaluating the use of masks among lay persons in the community and health care workers for preventing the spread of respiratory virus infections, including SARS-CoV-2, the virus that causes COVID-19. The update includes 739 citations that were published from early October to early December 2020 using the same search strategies as the original review. One study on the use of masks and the prevention of SARS-CoV-2 infection in a community setting (the DANMASK trial) and two studies in health care settings were added for the update.
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The DANMASK trial, a good-quality, open-label trial of 6,024 community-dwelling adults in Denmark evaluated the effects of wearing a surgical mask outside of the house, at a time when mask wearing in the community was neither recommended nor common. The trial found that the incidence of SARS-CoV-2 infection among participants was 2.0%. Mask use versus no mask use was associated with a small, non-statistically significant reduction in risk for SARS-CoV-2 infection. The trial was not designed to assess the effects of mask use as source control; in addition, high adherence to other infection control measures (for example, physical distancing and handwashing) could have attenuated potential benefits.

The evidence on mask use in health care settings and risk for SARS-CoV-2 infection was previously assessed as insufficient on the basis of three studies with methodological limitations. Two new cohort studies, both done in the United States, reported on mask use in health care settings. One study of 16,397 health care workers and first responders (86% health care workers) found that use of an N95 or surgical mask all of the time versus not all of the time was associated with a decreased risk for infection. In the second study, done in 20,614 asymptomatic health care workers, risk for infection was reduced with any mask use versus no mask use. An N95 mask was associated with decreased risk versus a surgical mask. However, both studies had methodological limitations, so evidence for various comparisons about mask use in health care settings and risk for SARS-CoV-2 remains insufficient.

Media contacts: A PDF for this article is not yet available. Please click the link to read the full text. The lead corresponding author, Roger Chou, MD, can be reached through the Oregon Health & Sciences newsroom at


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