Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection - California, February-December 2021

The use of face masks or respirators (N95/KN95) is recommended to reduce transmission of SARS-CoV-2, the virus that causes COVID-19 (1). Well-fitting face masks and respirators effectively filter virus-sized particles in laboratory conditions (2,3), though few studies have assessed their real-world...

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Bibliographic Details
Published in:MMWR. Morbidity and mortality weekly report 2022-02, Vol.71 (6), p.212-216
Main Authors: Andrejko, Kristin L, Pry, Jake M, Myers, Jennifer F, Fukui, Nozomi, DeGuzman, Jennifer L, Openshaw, John, Watt, James P, Lewnard, Joseph A, Jain, Seema
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
California - epidemiology
Case-Control Studies
Child
Child, Preschool
Communicable Disease Control - methods
Coronaviruses
COVID-19
COVID-19 - diagnosis
COVID-19 - prevention & control
COVID-19 Testing
COVID-19 vaccines
Disease transmission
Effectiveness
Face
Female
Full Report
Health aspects
Humans
Immunization
Infant
Infection
Infections
Laboratories
Male
Masks
Middle Aged
N95 Respirators
Protective equipment
Public health
Respirators
SARS-CoV-2
Self report
Severe acute respiratory syndrome coronavirus 2
Viral diseases
Viruses
Young Adult
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Summary:The use of face masks or respirators (N95/KN95) is recommended to reduce transmission of SARS-CoV-2, the virus that causes COVID-19 (1). Well-fitting face masks and respirators effectively filter virus-sized particles in laboratory conditions (2,3), though few studies have assessed their real-world effectiveness in preventing acquisition of SARS-CoV-2 infection (4). A test-negative design case-control study enrolled randomly selected California residents who had received a test result for SARS-CoV-2 during February 18-December 1, 2021. Face mask or respirator use was assessed among 652 case-participants (residents who had received positive test results for SARS-CoV-2) and 1,176 matched control-participants (residents who had received negative test results for SARS-CoV-2) who self-reported being in indoor public settings during the 2 weeks preceding testing and who reported no known contact with anyone with confirmed or suspected SARS-CoV-2 infection during this time. Always using a face mask or respirator in indoor public settings was associated with lower adjusted odds of a positive test result compared with never wearing a face mask or respirator in these settings (adjusted odds ratio [aOR] = 0.44; 95% CI = 0.24-0.82). Among 534 participants who specified the type of face covering they typically used, wearing N95/KN95 respirators (aOR = 0.17; 95% CI = 0.05-0.64) or surgical masks (aOR = 0.34; 95% CI = 0.13-0.90) was associated with significantly lower adjusted odds of a positive test result compared with not wearing any face mask or respirator. These findings reinforce that in addition to being up to date with recommended COVID-19 vaccinations, consistently wearing a face mask or respirator in indoor public settings reduces the risk of acquiring SARS-CoV-2 infection. Using a respirator offers the highest level of personal protection against acquiring infection, although it is most important to wear a mask or respirator that is comfortable and can be used consistently.
ISSN:0149-2195
1545-861X
DOI:10.15585/mmwr.mm7106e1