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Outbreaks, Alerts and Hot Topics

August 2021

The Call for Masks


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Column Editor: Angela Myers, MD, MPH | Director, Division of Infectious Diseases | Professor of Pediatrics, UMKC School of Medicine | Medical Editor, The Link Newsletter


It seems silly to me that one year later we are having a debate about masking in schools, when this time last year we were working hard to make sure kids even had an option to go to school in person. Many districts have now made decisions on whether (or not) to mandate masking for this upcoming school year, which has already begun in some parts of the metro area. Let’s do a quick recap on where we are in terms of school masking,1,2 summarized in Table 1, and what the data on effectiveness of masks tells us to this point.

Quite a few schools in the Kansas City metro area are requiring masks for school attendance with some notable exceptions. The Gardner-Edgerton School District is requiring masks only for kindergarten through 6th grade.3 Spring Hill is following the Johnson County mask regulations and requires masks from kindergarten through 8th grade,4 and the Lawrence School District is requiring masks only for unvaccinated students. It isn’t clear how this will be achieved since they are not documenting vaccination status.5 For schools and districts that are recommending mask use or have stated it is optional, it will be important to monitor COVID-19 cases and exposures with careful contact tracing.

While some still argue the science, the data on cloth masks overwhelmingly shows that they work to prevent the spread of infection. First, cloth masks are very effective at blocking large respiratory droplets that occur with normal speech (20 to 30 microns),6 and multi-layer cloth masks can block some aerosols (<10 microns) as well. Aerosols increase with louder speech and singing.7,8 Second, cloth masks are actually quite good at filtration, thus reducing the wearer’s exposure to others’ respiratory droplets and aerosols. We now know that multiple layers of fabric with a high weave density (sort of like a high thread count sheet) can filter up to 50% of tiny particles (<1 micron).9,10 In addition to laboratory simulations to assess prevention of droplet transmission and mask filtration ability, there is good real-world data that mask use works, with over 20 published papers in settings including households, salons, airplanes, and even military ships. Table 2 highlights some of the most pertinent (but certainly not all) data. 

Most adults agree that school is the best place for kids to learn and socialize. We are now entering the third school year of this pandemic, the likes of which had not been seen for 100 years. Masks were recommended in the 1918 influenza pandemic, just like they are being recommended now. We know masks are safe for nearly all people to wear,11 barring any neurologic or physical disability preventing the child from putting on and taking off the mask, or developmental delay making mask wearing unsafe or ineffective (e.g., severe autism). Finally, we also know that when kids wear masks in school, there is limited transmission of infection.12,13 Let’s hope that with these measures in place we can keep kids in school safely every day, all day, for this entire school year. And a potential silver lining may be fewer other respiratory viruses circulating too.

Read tips for helping children wear a mask from our Parent-ish blog.


Table 1. Summary of mask requirements and recommendations for pre-K through 12th grade by school state and school district (as of 8/16/21).

Table 2. Summary of real-world effectiveness of mask use.



  1. Accessed on Aug. 12, 2021.
  2. Accessed on Aug. 16, 2021.
  6. Bandiera L., Pavar G., Pisetta G., et al. Face coverings and respiratory tract droplet dispersion. Royal Soc Open Sci. 2020; doi: 10.1098/rsos.201663.
  7. Lindsley WG, Blachere FM, Law BF, Beezhold DH, Noti JD. Efficacy of face masks, neck gaiters and face shields for reducing the expulsion of simulated cough-generated aerosols. Aerosol Sci Technol. 2021. 55:449-457.
  8. Verma S, Dhanak M, Frankenfield J. Visualizing the effectiveness of face masks in obstructing respiratory jets. Phys Fluids (1994). Jun 1, 2020;32(6):061708. doi:10.1063/5.0016018.
  9. Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, Guha S. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS nano. May 26, 2020;14(5):6339-6347. doi:10.1021/acsnano.0c03252.
  10. Long KD, Woodburn EV, Berg IC, Chen V, Scott WS. Measurement of filtration efficiencies of healthcare and consumer materials using modified respirator fit tester setup. PLoS One. 2020;15(10):e0240499. doi:10.1371/journal.pone.024049.
  11. Shein SL, Whitticar S, Mascho KK, Pace E, Speicher R, Deakins K. The effects of wearing facemasks on oxygenation and ventilation at rest and during physical activity. PLoS One. 2021;16(2):e0247414. doi:10.1371/journal.pone.0247414.
  12. Zimmerman KO, Akinboyo IC, Brookhart MA, et al. Incidence and secondary transmission of SARS-CoV-2 infections in schools. Pediatrics 2021;147(4). doi:10.1542/peds.2020-048090.
  13. Dawson P, Worrell MC, Malone S, et al. Pilot investigation of SARS-CoV-2 secondary transmission in kindergarten through grade 12 schools implementing mitigation strategies–St. Louis County and City of Springfield, Mo., December 2020. MMWR Morb Mortal Wkly Rep 2021;70(12):449-455. doi:10.15585/mmwr.mm7012e4.
  14. Hendrix MJ, Walde C, Findley K, Trotman R. Absence of apparent transmission of SARS-CoV-2 from two stylists after exposure at a hair salon with a universal face covering policy–Springfield, Mo., May 2020. MMWR Morb Mortal Wkly Rep. Jul 17 2020;69(28):930-932. doi:10.15585/mmwr.mm6928e2.
  15. Wang Y, Tian H, Zhang L, et al. Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China. BMJ Glob Health. May 2020;5(5)doi:10.1136/bmjgh-2020-002794.
  16. Payne DC, Smith-Jeffcoat SE, Nowak G, et al. SARS-CoV-2 infections and serologic responses from a sample of U.S. Navy service members–USS Theodore Roosevelt, April 2020. MMWR Morb Mortal Wkly Rep. Jun 12, 2020;69(23):714-721. doi:10.15585/mmwr.mm6923e4.
  17. Freedman DO, Wilder-Smith A. In-flight transmission of SARS-CoV-2: a review of the attack rates and available data on the efficacy of face masks. J Travel Med. Sept. 25, 2020;doi:10.1093/jtm/taaa178.
  18. Van Dyke ME, Rogers TM, Pevzner E, et al. Trends in county-level COVID-19 incidence in counties with and without a mask mandate–Kansas, June 1-Aug. 23, 2020. MMWR Morb Mortal Wkly Rep. Nov 27, 2020;69(47):1777-1781. doi:10.15585/mmwr.mm6947e2.