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Evidence Summary

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Wearing 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)

 




Glossary

Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

Related Web Resources

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