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The Science of Mask-Wearing Hasn’t Changed. So Why Have Our Expectations?

Before every fashion retailer was selling their own cloth face covering, before a piece of fabric over your nose and mouth became a personal political statement, and before Goldman Sachs was saying a national face mask mandate is as good as a lockdown, Lara Martin was unsure whether homemade cloth masks were even a good idea.

The executive director of the United Methodist Committee on Relief, Martin was one of the people I interviewed back in March for a story about the science of masks. Back then, I found that masks were an excellent example of the scientific uncertainties swirling around the novel coronavirus. Remember, the Centers for Disease Control and Prevention and the surgeon general once told the general public not to wear masks. The data that existed on mask effectiveness largely dealt with medical respirators and surgical masks. It wasn’t clear how protective a cloth mask would be, and Martin worried that wearing masks might lead people to feel more safe than they actually were — and make choices that increased their risk of contracting or transmitting COVID-19.

Today, a lot has changed. But the science around cloth masks hasn’t.

Yes, the CDC now recommends cloth face coverings, the surgeon general starred in a video showing how to make them, and many businesses, and even cities, require them. Martin herself owns three and wears one every time she goes outside. But she told me that’s not because the evidence has significantly improved. “I don’t know enough, I don’t see enough evidence. Nothing has changed except that I care about my neighbors, I care about my colleagues, I care about people I don’t even know that I come across at the grocery store,” she said. “I am now saying to my community that I care about them, and that actually feels important to me as a scientist.”

Cloth and DIY face masks sit at the intersection where scientific data, public perceptions, and political opinions crash headlong into each other. Making smart decisions isn’t just about having data — it’s also about how we interpret the data we have. Safety moves along a spectrum with different relative levels of risk. Behavioral norms also matter, regardless of how much evidence backs them up. In the midst of a pandemic, masks are a reminder that science is seldom as simple, or as certain, as we want it to be — and that reasonable public health recommendations are sometimes based on more than just data.


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Do cloth face coverings work? Probably, to some extent. But just how much they work depends on the material, how they’re used, and what you’re expecting them to accomplish. And — regardless of what you’ve seen in highly shareable memes — we definitely don’t know enough to say that wearing these kinds of coverings will reduce risk of transmission by a specific percentage, let alone a high percentage. Those were the conclusions of an expert report published by the National Academies of Sciences on April 8, and two of the lead authors of that paper recently told me the science hasn’t significantly changed since then. Some studies have come out showing a correlation in certain regions between mask mandates and reduced spread of the coronavirus, but several of those not-yet-peer-reviewed studies have turned out to have important flaws — such as failing to account for factors like other behaviors (such as higher rates of social distancing) that went along with wearing masks in those places.

Instead, experts say what has changed is how both the public and public health institutions interpret this situation and the data surrounding it.

[Related: Where The Latest COVID-19 Models Think We’re Headed — And Why They Disagree]

“Back in March, it was difficult to even have anybody take you seriously when the CDC and WHO said the opposite,” said Jeremy Howard, a data scientist and entrepreneur who has become a major advocate of universal mask requirements. In response to the lack of support, he launched a bipartisan campaign called Masks4All that lobbied for widespread mask-wearing and argued that masks were a crucial, if not the most important, part of the COVID-19 response.

But Howard has also seen changes in how political actors interpreted his message. Back in March, he told me, before not wearing a mask became a signifier of conservative politics, Howard actually got the most traction talking about the need for masks on conservative news shows. “Going against the CDC was very on brand,” he said. “I was on “The Laura Ingraham Angle” talking about important masks were, and she was all for it.”

[Related: What To Look For In A Face Mask, According To Science]

When the political alignments shifted, that support vanished. Although a majority of Americans report wearing masks regularly, those numbers are 16 percentage points lower among Republicans compared to Democrats. In the last week, that’s begun to shift again, with Republican leaders advocating for mask use and criticizing President Trump for not wearing one. The politicized landscape has also made it difficult to have a nuanced conversation about mask effectiveness, experts said. Public health officials who issued mandatory mask-wearing orders have found themselves hounded by intense criticism and even death threats. More than two dozen have resigned in recent weeks.

At the same time, Michael Osterholm, a public health and disease expert who is worried that mask effectiveness is being over-hyped, has also found himself threatened and harassed. Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told me he’s received vulgar emails from people who read his statements questioning the efficacy of cloth masks. Osterholm said that his position was not that masks shouldn’t be worn — he wears one in public, himself — but that there is limited data on how effective DIY cloth masks are at stopping small particles, either from passing through or being forced out the sides of the mask. Without that information, he said, physical distancing and isolation remain the most important tools in stopping the spread of the coronavirus. But as more Republicans say the worst of the coronavirus is behind us, and usage of masks tracks tightly along the partisan spectrum, Osterholm told me he felt like well-meaning people were making him out to be a pandemic denialist.

The on-off, yes-no nature of this debate has also been frustrating for Dr. Marcella Nunez-Smith, a professor of medicine and epidemiology at Yale. Circumstances may mean that for some people the benefits of wearing a mask may not outweigh the risks. “There are conversations in a lot of Black and brown communities … ‘[Does] the risk and threat in terms of personal safety go up wearing a mask because of police action and being seen as a threat?’” she said.

[Related: For Black Americans, Wearing A Mask Comes With Complicated Anxieties]

At the same time, though, Nunez-Smith said masks might actually be more important for those communities because the distancing and isolation favored by experts like Osterholm hasn’t really been possible. Black workers are more likely than other workers to have jobs that are classified as essential. Because of that, reopening means something different for predominantly Black neighborhoods than it does for white neighborhoods. That also applies to the idea of social distancing and how practical that even is — something that could account for why self-reported mask usage is higher among nonwhite Americans, despite the possible police risk. “These are important contextual conversations,” Nunez-Smith said.

Ultimately, experts said, all the nuance and complication around masks is a challenge that public health messaging has to face up to. It’s difficult to make one-size-fits-all recommendations for situations that don’t readily lend themselves to a one-size-fits-all reality.

[Related: How Americans View The Coronavirus Crisis And Trump’s Response]

The good news is that there’s more agreement than disagreement on where to start. Just look at Osterholm and Howard, two experts who might easily be seen as having opposing viewpoints in this battle. Yet they hold similar positions on one issue: They both wish the CDC would have given the public the nuanced information about masks back in March and trusted them to understand it. Granted, that might mean presenting the public with a complex message, such as: “We don’t know how well cloth masks work, so distancing should come first, but masks are likely to work to some extent and not everyone can distance themselves.” That’s a mouthful and harder to fit on a bumper sticker than “yes, you should,” or “no, you shouldn’t.” But it comes down to what builds trust more: certainty or honesty?

“We owe it to the public to help them understand what kind of protections they’re getting,” Osterholm said. “We owe it to the public to tell them what we know.”



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Maggie Koerth is a senior science writer for FiveThirtyEight.

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