Evidence Summary
What is an Evidence Summary?
Key messages from scientific research that's ready to be acted on
Got It, Hide thisWearing masks reduces transmission of respiratory viruses
Liang M, Gao L, Cheng C, et al. Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis. Travel Med Infect Dis. 2020;36:101751.
Review question
Do masks prevent transmission of respiratory viruses?
Background
Many respiratory illnesses, such as severe acute respiratory syndrome (SARS) and Coronavirus Disease 2019 (COVID-19), are caused by viruses that may spread through respiratory droplets. Masks may block particles that are larger than the micropores in the mask. However, it is uncertain whether masks prevent transmission of respiratory illnesses from one person to another.
How the review was done
The researchers did a systematic review of studies available up to March 2020. They found 21 studies with 8,686 people, including 6 randomized controlled trials.
The key features of the studies were:
- included people were health care workers and non–health care workers (including relatives of patients);
- masks included paper or cotton masks, surgical masks, and medical masks (N95);
- people were tested for respiratory viruses in general, severe acute respiratory syndrome coronavirus (SARS-CoV), influenza (including H1N1), and SARS-CoV-2 (COVID-19); and
- respiratory virus infection was confirmed by laboratory testing.
What the researchers found
Wearing masks reduced the risk that people became infected by respiratory viruses. The risk was reduced for both health care workers and non–health care workers.
Conclusion
Wearing masks reduces the transmission of respiratory viruses. This review did not report infection rates separately for different types of masks, so some mask types may be more protective than others. Masks are not a substitute for social distancing and frequent hand washing.
Masks vs control to prevent transmission of respiratory viral infection
| Group of people | Number of studies (and people) | Effect of masks vs no masks on the rate of respiratory viral infection |
| All people | 21 studies (8,686 people) | 62 fewer people out of 100 got infections (from as few as 46 to as many as 74) |
| Not health care workers | 8 studies (3,820 people) | 44 fewer people out of 100 got infections (from as few as 19 to as many as 61) |
| Health care workers | 12 studies (4,751 people) | 78 fewer people out of 100 got infections (from as few as 60 to as many as 88) |
Related Topics
Glossary
Studies where people are assigned to one of the treatments purely by chance.
A comprehensive evaluation of the available research evidence on a particular topic.
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