Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US

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Tune into another episode of Avalere’s Journal Club Review podcast series on Avalere Health Essential Voice. In this segment, our health policy experts discuss a recent study on the effectiveness of statewide mask mandates in reducing the spread of COVID-19, and the implications of its findings on future policy interventions.
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“Having a view into the effects of different interventions is critical for policymakers as they pursue pandemic response efforts.” Nick Diamond


Nick Diamond , Consultant II

Nicholas J. Diamond, JD, LLM, MBe, provides strategic counsel on health policy and market access issues spanning US (federal, state, and local) and international markets.

This interview was originally published as a podcast. The audio is no longer available, but you can read the transcript below. For updates on our newly released content, visit our Insight Subscription page.


Nick: Hello, and welcome to another episode in the Avalere Health Essential Voice series focused on the findings and themes from Avalere’s Journal Club. In this series, we provide commentary on a contemporary healthcare publication that was presented at our internal Journal Club meeting.

My name is Nick Diamond and I’m one of our public health policy experts here at Avalere. Joining me today is my colleague, Associate Madison Switalla.

In today’s episode, we’ll be debriefing on the article entitled “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” authored by Wei Lyu and George L. Wehby and published in the June 2020 Journal of Health Affairs.

Let’s dive right into the content of the article. Maddie, can you explain a little about the study to our listeners? What was the research team’s objective? What were they measuring, and what were they not measuring?

Madison: Sure, thanks. The study examines the degree to which statewide face mask mandates contributed to a reduction in the spread of COVID-19 in the states that issued them compared to the states that didn’t during a period from March 31 to May 22, 2020. It compared daily county-level COVID-19 growth rates in terms of case counts using a regression model that controls for other factors like social distancing measures, population density and population age.

Researchers found that statewide public mask mandates reduced the rate of COVID-19 cases to a statistically significant degree, with their model suggesting between 230,000 and 450,000 additional cases of the virus were avoided. This produced increasing returns the longer the mask mandates were in place, which means that case counts dropped at an increasingly greater rate with each passing day that the statewide mask mandates were in place.

While this leads to the conclusion that masks are generally effective at slowing the spread of COVID- 19, it’s important to note here that the study is measuring what they call “intent to treat” of the mask mandates, meaning that researchers were measuring the intended effect of that public policy within the state rather than measuring the specific effectiveness of any individual mask. People use different masks, and even an N95 mask is not perfectly effective. Now is a good time to mention to please continue to stay home if you’re sick.

More importantly, the study is not measuring mandate compliance. As I’m sure our listeners have seen, some people subvert mask mandates in states that have them, and others wear masks in states that don’t. There are also people who wear them inconsistently or incorrectly in both types of states.

It’s been about two months since this journal article was published, and about three since the period that the study examined. So, what is the role of studies like this in the current debate over COVID-19?

Nick: Maddie, I would say studies like this are really very important, particularly when we look at the trajectory of a pandemic. Having a view into the effects of different interventions is critical for policymakers as they pursue pandemic response efforts. As we’ve seen, masks play a central role as states have begun considering reopening plans, and we’ve seen rather significant differences state-to-state in that regard.

Madison: Studies like this help us understand the importance of masks independent of other social distancing measures, because small efforts like this can and do add up. The authors can add more relevant information to this study as time goes on, or additional considerations if they choose, to help us get a better sense of what social distancing measures are the most effective and worth pursuing as we continue into the future.

Nick: I do think it’s a good lesson for how we think about measuring the impact of different policy interventions. So often in public health, and this holds true for the current pandemic, we’re not just looking at a single potential intervention. We’re looking at a spectrum of interventions that ideally will all work in concert.

So, Maddie, what do you think this study tells us about designing different policy interventions as we consider options to mitigate the spread of COVID-19?

Madison: To be most effective in any policy recommendation, there are many things to consider, such as what you can measure and what you can’t, or identifying limitations. We consider certain parameters in our policy work, but it’s important to think about where your measurements must stop. There are conflating factors that go into any policy recommendation and it’s important to know what you cannot consider and factor into your decisions.

Similarly, we should also be aware of the context around our recommendations. The realities of the policy environment that you’re operating in impact what you’d like to accomplish and the considerations that come along with the implementation of any policy intervention.

This leads us to enforcement of policy interventions. Are carrots or sticks, rewards or penalties, or a combination of both, the most appropriate for any given intervention? Vaccine access is a great example of this. It’s been an issue for years and will continue to be as a COVID-19 vaccine rolls out.

And lastly, I’d say evaluating the role of government in a given policy intervention situation, whether it be comparing the appropriateness of federal versus state or local intervention or public private partnerships, and figuring out what can be leveraged in those spaces to implement whatever solution that you’re recommending.

Nick: Absolutely, all very relevant points. And Maddie, with that in mind, what best practices do you think we can learn from the study’s conclusions as we think about responding to epidemics and pandemics in the future?

Madison: As I said, it has been several months since this study came out, and mask usage hasn’t become ubiquitous across the United States in that time. With that in mind, it’s important to think about consistency in messaging, having alignment between those different federal, state and local government sources. Neighboring states even need consistency, and alignment with the private sector is important as well as you try to get every person on board with the recommendation.

The messaging of public health recommendations is just as important as the policy intervention itself. We can think of many ways how the implementation of a policy recommendation doesn’t play out in the way it’s intended or designed. And so, thinking about that messaging to the public, especially if a policy intervention requires public cooperation, is especially important.

From there, it’s important to think about how policy interventions are based on the best available evidence at any given point in time, and how it’s essential to be flexible with those recommendations based on updated information. Public health authorities, researchers and others do their best to reference the best available evidence, but it’s good, especially when working with the public, to admit up front that things can change. That can help with any sort of wider policy recommendation, and hopefully with future pandemic responses going forward.

Nick: Absolutely. Well, Maddie thanks so much for joining me today to talk about this rather important article and reflect a little bit on its implications for the ongoing pandemic. I think your insights have been really valuable and I know our listeners appreciate it. And for our listeners, thanks for tuning in to the Avalere Health Essential Voice Journal Club Review. Please stay tuned for future episodes in this Journal Club series. If you’d like to learn more, please visit us at Thanks, and be well.

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