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Dramatic Results of Natural Experiment with Face Masks

A natural experiment with face masks in Kansas and another in Tennessee demonstrate their effectiveness in slowing the spread of COVID-19.
Dramatic Results of Natural Experiment with Face Masks
Shopping, sale, consumerism and people concept – happy couple wearing face protective medical masks for protection from virus disease with food basket at grocery store or supermarket showing thumbs up

Face masks continue to be a hot button issue for many Americans. There have been relatively few controlled experiments to test their effectiveness against the transmission of COVID-19. That’s because it would be unethical to intentionally expose people to the coronavirus. But a natural experiment with face masks in Kansas and another in Tennessee have produced results suggesting that masks reduce the transmission of COVID-19.

The Kansas Unplanned Natural Experiment with Face Masks:

In July, Governor Laura Kelly issued a mandate to all Kansas residents. They were supposed to wear face masks in public if they could not maintain a distance of more than 6 feet from other people.

Just because the Governor issued a mandate does not mean it was adopted. There are 105 counties in Kansas. Commissioners in 80 counties flat out rejected the mandate. Government leaders in four counties did not thumb their noses at the governor but they opted to ignore her mandate. Although some of the remaining 21 counties were a bit slow adopting the mask mandate, they are now all on board.

What this amounts to, then, is an unplanned natural experiment with face masks. Researchers at the University of Kansas tracked the incidence of COVID-19 across the state. On October 25, 2020, the KU Institute for Policy & Social Research issued a report titled “Do Masks Matter in Kansas?”

The Answer: Masks Work in Kansas!

To appreciate the effectiveness of face masks in Kansas you really need to look at the curves. Here is a link. What you will see is that the mandate went into effect on July 3, 2020. On the graph, that is noted by a red line. According to the report:

“Counties with a mask mandate saw a decrease starting 14 days after the mandate.

“Mask counties held cases flat.”

“No-Mask counties steadily increasing.”

The investigators ask this question:

Do Masks Work in Kansas?

Their answer:


“We Found a 50% reduction in the spread of COVID-19 in counties that had a mask mandate compared to those without.

“Masks do not eliminate COVID, but they significantly slow the spread of the disease.”

In the 80+ counties where officials did not adopt the mask mandate, cases climbed from 10 per 100,000 residents to almost 40 per 100,000. In the counties where the mask mandate was adopted, cases have plateaued since July at approximately 20 per 100,000 residents.

The lead investigator noted that a:

“50% reduction in a virus that is very contagious is huge.”

Although masks did not provide perfect protection, they did slow the spread of the virus in places that tried to follow the governor’s directive. Now that Kansas is experiencing record high levels of COVID-19 like so many other states, the governor is hoping the legislature will reinforce her statewide mask mandate.

The Tennessee Unplanned Natural Experiment with Face Masks:

The experiment in Tennessee was different from the one in Kansas, but the outcome was similar. Governor Bill Lee did not issue a mask mandate for his state. Instead, he gave the counties discretion to decide for themselves what they wanted to do.

Here is a quick overview from a report from Vanderbilt School of Medicine Department of Health Policy (Oct. 27, 2020).

“There has also been considerable COVID-19 policy activity at the local and state level. As of this writing, just over half (54%) of Tennesseans are subject to a mask requirement in their county, while the remaining 46% either never faced a masking requirement (31%) or were only subject to a requirement during the summer months (July-September; 15%). In addition, as of September 30, all restrictions on group gatherings and on business capacity and operations were lifted in 89 counties where, collectively, 60% of the state population resides.”

Again, we encourage you to look at the graphs so you can see for yourself what has happened in Tennessee. Here is a link.

Counties With Mask Requirements vs. Counties Without Mask Requirements:

Here, in the words of the investigators, are the results of this natural, unplanned experiment:

“Hospitals that predominantly serve patients from areas without masking requirements continue to see the highest rate of growth in hospitalizations. As the percentage of patients residing in mask-requirement counties increases, the growth curve ‘flattens,’ indicating much lower growth in hospitalizations. It is also clear that masking alone is not a siver bullet: since early October nearly every region of the state has seen growth in hospitalizations. Again, however, this growth has been most dramatic in hospitals that draw a large percentage of patients from areas without mask requirement.”

What Are the Conclusions of This Natural Experiment with Face Masks?

The authors of the report conclude:

“An important takeaway from this analysis is that areas with virus mitigation strategies—including but not limited to masking requirements—have seen lower growth in hospitalizations since the summer months; hospitals in these areas are in a much better position to serve the entire spectrum of community health needs, not just COVID-19 patients…

“A comprehensive set of interventions–potentially including targeted restrictions that limit indoor contacts coupled with support for affected industries–and certainly including greater mask use, social distancing and hygiene, is most likely to be effective at bringing the virus into better control and consumers back to local businesses. Policies and individual behavior that facilitate letting the virus go unchecked in our communities will not only result in poorer health outcomes, but risks creating unnecessary and costly headwinds for families, businesses, schools, and health care providers across the state.”

The People’s Pharmacy Perspective on the Natural Experiment with Face Masks:

Masks are not magic bullets. They won’t prevent all cases of COVID-19. Some masks are much better than others. Some people wear them correctly while others allow their masks to slip below their noses. But until we have effective vaccines and/or successful treatments, we do not have other strategies that will slow the growth of the COVID-19 pandemic.

We welcome your thoughts in the comment section below. If you know people who are convinced face masks are a waste of time, you might want to share this article by scrolling to the top of the page and sending it via email, Facebook or Twitter. Thank you for supporting our work. 

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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