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The Research Behind Masks

Elmbrook's Medical Advisory Board has reviewed and discussed many of the studies linked below related to the positive impact (less disease spread) of masking. In addition to these research studies, we have also observed very little presence of the flu, strep throat, and other typical viruses that appear in our schools during the winter months. These observations have been confirmed by the doctors on our advisory board as patterns also experienced in the three different hospital systems they represent. 

Here are several articles from well-respected sources around the world. 

  1. Centers for Disease Control and Prevention:

  1. Effects of universal masking on Massachusetts healthcare workers' COVID-19 incidence (Lan FY, Christophi CA, Buley J, Iliaki E, Bruno-Murtha LA, Sayah AJ, Kales SN. Occup Med (Lond). 2020 Dec 12;70(8):606-609. doi: 10.1093/occmed/kqaa179. PMID: 33225363; PMCID: PMC7665621.)

  2. Proceedings of the National Academy of Sciences: An evidence review of face masks against COVID-19

  3. World Health Organization: Advice on the use of masks in the context of COVID-19

  4. COVID-19 Cases and Transmission in 17 K-21 Schools - Wood County, Wisconsin, August 31-November 29, 2020

  5. Finally, several research studies referenced in a current medical database review:

Rationale — The rationale for all individuals (regardless of symptoms) to wear a mask in the community is primarily to contain secretions of and prevent transmission from individuals with infection, including those who have asymptomatic or presymptomatic infection. Masks can also reduce exposure to SARS-CoV-2 for the wearer.

● Source control – Several studies support the use of masks to provide source control and reduce transmission in the community [193,199-206]. In a retrospective study of 124 patients with confirmed COVID-19 and their families in Beijing, China, secondary transmission occurred in 41 families; use of masks by family members (including the index patient) prior to illness onset in the index patient was independently associated with a reduced risk of infection [199]. The type of mask used (medical or cloth) was not specified. In a case report of two hair stylists with COVID-19 who worked while symptomatic prior to the diagnosis but wore face coverings, there were no subsequent COVID-19 diagnoses among 139 clients with close contact, all of whom were also wearing face coverings; both medical masks and cloth face coverings were used [207]. In epidemiologic studies, government-issued mask mandates and high rates of self-reported mask wearing have each been associated with decreased community incidence rates [206,208]. Although limited by assumptions and estimates, modeling studies have also suggested that high adoption of mask-wearing by the general public can reduce transmission, even if masks are only moderately effective in containing infectious respiratory secretions [209,210].

● Prevent exposure – Mask-wearing in the community may also be associated with protection for the wearer [211-213]. In a report of 382 service members who were surveyed about personal preventive strategies in the setting of a SARS-CoV-2 outbreak on a United States Navy aircraft carrier, self-report of wearing a face cover was independently associated with a lower likelihood of infection (odds ratio [OR] 0.3), as were avoiding common areas (OR 0.6) and observing social distancing (OR 0.5) [211]. In a retrospective analysis of 1060 individuals identified by contact tracing following clusters of infections in Thailand, wearing a mask all the time was associated with a lower odds of infection compared with not wearing a mask; there was no significant association between wearing a mask some of the time and infection rate [212]. A randomized trial from Denmark did not identify a decreased rate of infection among individuals who were provided with surgical masks and advised to wear them when outside of the house for a month (1.8 versus 2.1 percent among individuals who were not given masks or the recommendation) [214]; however, clear conclusions about mask efficacy cannot be made from this study because of a low rate of community transmission during the time of the study and other limitations.

Mask-wearing has also been hypothesized to reduce the viral inoculum, even if it doesn't eliminate exposure, and thereby reduce the risk of severe illness [215,216].