The Science Behind Masks

For those who question whether masks work, here are several scientific experiments and studies that support the recommendation that we should all be wearing masks when out in public.

The first four articles in the list are videos. The next one is a good summary of mask issues. Next are short excerpts from a variety of scientific articles, The last is a list of additional scientific studies that I found at the end!

Live Science

Visualization shows exactly how face masks stop COVID-19 transmission

https://www.livescience.com/face-mask-visualization-droplets-covid-19.html

It’s Ok to be Smart: How Well Do Masks Work?

“Wearing a mask ‘s OK to be Smis a cheap and easy way to help stop the spread of airborne infections like COVID-19. It’s also a sign that you want to help protect other people and have them protect you… that we’re all in this together. Here are some awesome slow-motion schlieren imaging experiments to demonstrate why masks work!”

https://www.pbs.org/video/how-well-do-masks-work-ke2qje/

It’s Ok to be Smart: COVID-19 & Mask Myths DEBUNKED!

https://www.youtube.com/watch?v=npXP5wqNzaI

Face Masks Greatly Reduce Risk of COVID-19: Watch This Video to See How

University of California San Francisco

Still Confused About Masks? Here’s the Science Behind How Face Masks Prevent Coronavirus

By Nina Bai

https://www.ucsf.edu/news/2020/06/417906/still-confused-about-masks-heres-science-behind-how-face-masks-prevent

The Journal of the Pediatric Infectious Diseases

“A Rosetta Stone for Understanding Infectious Drops and Aerosols”

Proceedings of the National Academy of Sciences of the United States of America (PNAS)

Identifying airborne transmission as the dominant route for the spread of COVID-19

https://www.pnas.org/content/117/26/14857?fbclid=IwAR13NBD0pDZhz65ahs3Ad5TjTe6zOW2A-4JHar0f7syYxPr1YGUqMfHdE14

Proceedings of the Royal Society – The Royal Society Publishing

A modelling framework to assess the likely effectiveness of facemasks in combination with ‘lock-down’ in managing the COVID-19 pandemic

Preprints 2020

Face Masks Against COVID-19: An Evidence Review

Howard, J.; Huang, A.; Li, Z.; Tufekci, Z.; Zdimal, V.; van der Westhuizen, H.; von Delft, A.; Price, A.; Fridman, L.; Tang, L.; Tang, V.; Watson, G.L.; Bax, C.E.; Shaikh, R.; Questier, F.; Hernandez, D.; Chu, L.F.; Ramirez, C.M.; Rimoin, A.W. Face Masks Against COVID-19: An Evidence Review. Preprints 2020, 2020040203 (doi: 10.20944/preprints202004.0203.v2).

“The science around the use of masks by the general public to impede COVID-19 transmission is advancing rapidly. Policymakers need guidance on how masks should be used by the general population to combat the COVID-19 pandemic. Here, we develop an analytical framework to examine an overlooked aspect of mask usage: masks as source-control targeting egress from the wearer with benefits at the population-level, rather than as PPE used for ingress control for health-care workers with focus on individual outcomes. We consider and synthesize the relevant literature to inform multiple areas: 1) transmission characteristics of COVID-19, 2) filtering characteristics and efficacy of masks, 3) estimated population impacts of widespread community mask use, and 4) sociological considerations for policies concerning mask-wearing. A primary route of transmission of COVID-19 is likely via respiratory droplets, and is known to be transmissible from presymptomatic and asymptomatic individuals. Reducing disease spread requires two things: first, limit contacts of infected individuals via physical distancing and other measures, and second, reduce the transmission probability per contact. The preponderance of evidence indicates that mask wearing reduces the transmissibility per contact by reducing transmission of infected droplets in both laboratory and clinical contexts. Public mask wearing is most effective at reducing spread of the virus when compliance is high. The decreased transmissibility could substantially reduce the death toll and economic impact while the cost of the intervention is low. Given the current shortages of medical masks we recommend the adoption of public cloth mask wearing, as an effective form of source control for now, in conjunction with existing hygiene, distancing, and contact tracing strategies. We recommend that public officials and governments strongly encourage the use of widespread face masks in public, including the use of appropriate regulation.”

https://www.preprints.org/manuscript/202004.0203/v2?fbclid=IwAR05TlsRjdXSDG9rD0GPpmQCF0Jpb-eWy39nCTk7YdcIyvjoAwyo75SL23w

The Lancet

Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis

Derek K Chu, MD; Prof Elie A Akl, MD; Stephanie Duda, MSc; Karla Solo, MSc; Sally Yaacoub, MPH; Prof Holger J Schünemann, MD, et al. Open AccessPublished:June 01, 2020DOI:https://doi.org/10.1016/S0140-6736(20)31142-9

“The findings of this systematic review and meta-analysis support physical distancing of 1 m or more and provide quantitative estimates for models and contact tracing to inform policy. Optimum use of face masks, respirators, and eye protection in public and health-care settings should be informed by these findings and contextual factors.”

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext?fbclid=IwAR2hyvUr-T327mi2nXF7xJu79vI0HLFds_I_heqn422GscK9T8K3nRi-L4Q

Heath Affairs

Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US

Wei Lyu and George L. Wehby PUBLISHED:JUNE 16, 2020 Free Access https://doi.org/10.1377/hlthaff.2020.00818

“State policies mandating public or community use of face masks or covers in mitigating novel coronavirus disease (COVID-19) spread are hotly contested. This study provides evidence from a natural experiment on effects of state government mandates in the US for face mask use in public issued by 15 states plus DC between April 8 and May 15. The research design is an event study examining changes in the daily county-level COVID-19 growth rates between March 31, 2020 and May 22, 2020. Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage-points in 1–5, 6–10, 11–15, 16–20, and 21+ days after signing, respectively. Estimates suggest as many as 230,000–450,000 COVID-19 cases possibly averted By May 22, 2020 by these mandates. The findings suggest that requiring face mask use in public might help in mitigating COVID-19 spread.”

https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818?fbclid=IwAR1VgtEd94iqaGgQ3Qqh902oGb9rgvj5Zsm-g2Z70R_XctoD9bJ4uKBXsgI&

Research Gate

Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks (Update June 15, 2020). 

Leffler, Christopher & Ing, Edsel & Lykins, Joseph & Hogan, Matthew & McKeown, Craig & Grzybowski, Andrzej. (2020). Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks (Update June 15, 2020)..

“Conclusions. Societal norms and government policies supporting the wearing of masks by the public, as well as international travel controls, are independently associated with lower per-capita mortality from COVID-19.”

https://www.researchgate.net/publication/342198360_Association_of_country-wide_coronavirus_mortality_with_demographics_testing_lockdowns_and_public_wearing_of_masks_Update_June_15_2020

Growing Body Of Evidence Suggests Masks Protect Those Wearing Them, Too

https://www.npr.org/2020/07/20/893227088/growing-body-of-evidence-suggests-masks-protect-those-wearing-them-too?fbclid=IwAR1KIf0QFf-z6z11L0ASd2FUnlCcqFaUTS1a1OF1bIcy9Q9aX46sazEJObw

And, now that I’ve gone this far, I found this list of “Recent Studies” from the CDC.

(Confession: I haven’t investigated these!)