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White House coronavirus response coordinator Deborah Birx speaks to reporters on September 30.
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Why every state should adopt a mask mandate, in 4 charts

The latest research suggests mask mandates help control the spread of Covid-19.

Deborah Birx, the coordinator of the White House coronavirus task force, toured North Dakota this fall, as the state was overwhelmed by one of the worst Covid-19 outbreaks in the country. While she commended the state’s testing efforts, she was distraught by the noticeable lack of face masks in public spaces. “This is the least use of masks that we have seen in retail establishments of any place we have been,” she said at an October 26 press conference.

North Dakota, which at the time didn’t require masks, had the lowest mask-wearing rate in the country in October, according to survey data.

North Dakota is not the only state that lagged in a mask policy in the throes of a major outbreak, however: Eight of the top 10 states that saw the highest new cases per capita in October did not have a widespread mask mandate, as the chart below shows. (Several of these Great Plains and Midwestern states were spared significant outbreaks of the virus until the fall.)

The chart shows that several states without mask mandates have seen big increases in Covid-19 cases in October. Youyou Zhou for Vox

But the dramatic surge of Covid-19 across the country this fall and winter has forced some states to change course. On November 8, Utah implemented a mask mandate, as new daily Covid-19 cases continue to rise in the state and across the country. Several other states have implemented or tightened mandates since then, including Iowa and North Dakota. Thirty-seven states now have mandates, according to the AARP.

And on December 4, the CDC issued a new recommendation that people wear masks indoors at all times, unless they are at home.

Over the course of the pandemic, America has been engaged in a massive and uncontrolled mask experiment: Some jurisdictions implemented and enforced mask mandates; others rejected them as public health guidance became politicized. President Donald Trump has repeatedly questioned and even scorned the use of masks, and several Republican governors have followed his lead. President-elect Joe Biden, meanwhile, has called for a national mask mandate and for Americans to wear masks for the “first 100 days” he is in office, as vaccines roll out.

But the different state-level approaches mean researchers can now parse the results of a trial they never would have received approval to conduct. New research from Kansas and Tennessee suggests that not only do mask mandates prevent Covid-19 spread, they may also blunt the severity of illness and reduce the number of serious cases that require hospitalization. Other findings support the argument more and more public health experts are making: that masks remain among our cheapest most effective tools to control the pandemic — if worn consistently.

“If you’re not in the ICU, the only tools at our disposal that we know work are the tried-and-true public health measures, like social distancing, hand-washing, and masks,” says Vin Gupta, a critical care pulmonologist and affiliate assistant professor for the Institute for Health Metrics and Evaluation at the University of Washington. “We’re bearing the brunt of those things being implemented poorly.”

“You’re less likely to get Covid-19 if you’re wearing a mask,” says Donna Ginther, an economist and director of the Institute for Policy and Social Research at the University of Kansas. And “even if you do get sick while wearing a mask, you’re less likely to get deathly ill.”

Let’s walk through some of the latest research on mask mandates and what it means as we head into one of the most perilous seasons in the pandemic so far.

New evidence from Kansas and Tennessee that mask mandates control the spread of Covid-19

One intriguing piece of evidence of the effect of mask mandates on controlling the spread of the virus comes from Kansas. In July, Laura Kelly, the Democratic governor of Kansas, issued a mandate requiring everyone in public places to wear a mask where 6 feet of social distancing couldn’t be maintained. It prompted an immediate outcry from conservatives. Because of a state law passed in June that allowed counties to supersede the governor’s emergency powers, 81 counties out of 105 opted out of the mask mandate altogether, and only 21 counties decided to enforce it.

Two researchers from the University of Kansas analyzed what happened next.

Youyou Zhou for Vox

Ginther, the economist working on this analysis, found that in the counties that enforced mask-wearing, new cases stayed roughly steady. But in the counties without mandates, even after controlling for how often people left their homes, they doubled. “We were stunned by the strength of the effect,” she says.

The public health officer of Johnson, the state’s largest county, was so impressed he asked Ginther to share her work with the Board of County Commissioners, even though it’s not yet peer-reviewed or even written up into a paper. She is currently working on publishing the results.

Ginther says it wasn’t until 12 weeks after the mandates took effect that the growth in cases began to slow. But she thinks her results are likely conservative. “A 50 percent reduction in cases is likely to be a lower-bound on the true effect of wearing a mask,” she says. “If you had 100 percent compliance, I would expect to see an even larger effect.”

Other researchers have made related findings. A nonprofit group called Prevent Epidemics recently published a report showing that, following mask mandates, coronavirus cases declined in Alabama, Oklahoma, South Carolina, and Texas. The CDC found that in Arizona, after a mask mandate was put in place, Covid-19 cases dropped 75 percent. Conversely, cases spiked 151 percent when stay-at-home orders were lifted, demonstrating that behavior has a significant impact on viral transmission.

In addition to slowing the spread of the virus, new evidence from Tennessee shows that mask mandates could reduce the severity of the virus. A paper by researchers at Vanderbilt found that at Tennessee hospitals where at least 75 percent of Covid-19 patients came from counties with mask requirements, coronavirus hospitalization rates are the same as they were in July. In hospitals where fewer than 25 percent of patients come from places with a mask mandate, hospitalizations are 200 percent higher. What’s more, the researchers wrote, hospitals in areas with mask requirements and other mitigation strategies “are in a much better position to serve the entire spectrum of community health needs, not just Covid-19 patients.”

Mask mandates lead to more people wearing masks

Even if they aren’t always followed, mask mandates appear to be an effective tool in encouraging behavior change. The Institute for Health Metrics and Evaluation (IHME) at the University of Washington found in August that mask use increased 8 percentage points after mask mandates, and increased 15 points if those mandates were enforced.

Only around 65 percent of Americans currently regularly wear masks, according to IHME. But in Singapore, for instance, around 95 percent of people wear masks, and they have one of the world’s lowest coronavirus death rates. “We know that countries that wear masks are doing much better,” says Ali Mokdad, the chief strategy officer of public health at the University of Washington.

Thirty-three states and Washington, DC, implemented statewide mask mandates between April and August. During the same period, an increasing number of Americans began to wear masks regularly, according to a weekly survey started in mid-April by the data intelligence company Premise.

This chart shows that masks have gradually become the norm from April to October. Youyou Zhou for Vox

There is one caveat of all the analyses mentioned above: They simply observe behavior, which means that they can demonstrate associations — like case counts falling after mask mandates are put in place — but not causation. The gold standard to prove that would be a randomized controlled trial. But that’s a hard study to design in a pandemic because of ethical concerns.

Even without randomized trials, Rebekah Gee, a public health policy expert and secretary of the Louisiana Department of Health, says the body of evidence “confirms what public health experts have known since early on in this pandemic, which is that masks work.”

Masks could save 130,000 lives by February, but more Americans would have to wear them consistently

In fact, a study published October 23 in Nature Medicine by IHME’s forecasting team modeled current public health interventions — projecting case numbers based on current behavior — and found that universal mask use could save as many as 130,000 lives by the end of February 2021.

Mokdad says that’s why it’s essential to have clear, consistent recommendations to wear masks. He adds, “We never debate seatbelts. Is it okay if only 80 percent of people wear them? We say everybody should.” But while he would prefer that 100 percent of people wear masks, Mokdad says at this point, any incremental increase in mask use “for me is a celebration.”

Unfortunately, in many parts of the US, mask use is actually decreasing. In Florida, for example, which grappled with a serious surge in cases this summer, Mokdad says 70 percent of people were wearing masks in August. Now, only 65 percent are. “Wearing masks has been a response to fear rather than a good, persistent behavior,” Mokdad says.

Vox analyzed the relationship between the frequency of wearing masks from the Premise survey data and the Covid-19 cases in states from April to October. As the charts below show, in states with mandates where cases surged in the spring, more people now wear masks. These states — where more people consistently wear masks — are now less likely to see another huge surge in cases.

This chart shows that mask mandates encourage consistent mask wearing, bringing down case numbers overtime. Youyou Zhou for Vox

Even though mask use has risen in many states, the nation as a whole is on a troubling trajectory, with new daily cases, hospitalizations, and deaths all on the rise. Mokdad says he’s very concerned about the holidays. “As we go be with our loved ones — our grandparents, our kids — do you want to go sit at a table and risk the people you care about most, or do you want to wear a mask?” IHME models predict that if some US states increased their mask use from now on, they could reduce the number of future Covid-19 deaths by about 50 percent.

The stakes for getting this right are high — not just for the holidays, but for the rest of the pandemic, however long that might be.

Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, recently echoed Biden’s call for a national mask mandate. “If you don’t want to shut down, at least do the fundamental, basic things,” Fauci told the editor-in-chief of JAMA, “the flagship of which is wearing a mask.”

Rather than thinking about a mask mandate as something that takes away a freedom, as anti-mask protestors have claimed, Leana Wen, a physician and the former Health Commissioner for the City of Baltimore, says, “Mask-wearing allows you to do things.” If everyone wears a mask, it will keep transmission low, allowing businesses and schools to stay open.

“If you want a more normal life, we need to adjust our behavior, as opposed to locking ourselves away,” Ginther says. “Masks rise to the top as an approach we can take as a society to have a more open economy but not get everyone sick.”

Lois Parshley is a freelance investigative journalist. Follow her Covid-19 reporting on Twitter @loisparshley.

Editor’s note, November 7: Due to a data error, a previous version of the chart of increases in Covid-19 cases in October did not include Hawaii and miscategorized Louisiana as not having a mandate. In fact, Louisiana implemented a mandate in August. The chart has been updated to reflect these changes.

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