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Study: States With Mask Mandates Saw Fewer Summertime COVID Cases

Crowd wearing face masks.

Nadzeya_Dzivakova / Getty Images

Key Takeaways

  • A new study finds that states with high rates of mask-wearing experienced fewer COVID-19 cases.
  • States with mask mandates saw higher mask adherence.
  • Fully vaccinated people should continue following CDC guidelines, including wearing their masks in crowded areas and when around unvaccinated people. 

Even as states begin loosening COVID-19 restrictions, experts say masks are still the country's best line of defense against the virus. A recent study shows that states with high levels of mask-wearing reported fewer COVID-19 cases last summer.

Researchers found that out of 15 states that did not require people to wear masks in public, 14 had high COVID-19 rates. Meanwhile, the eight states that reported 75% or more mask adherence between June 2020 and September 2020 did not have high COVID-19 rates. The findings were published in the journal PLOS One in April.

States with more than 200 COVID-19 cases per 100,000 residents were considered to have a high case rate.

The Centers for Disease Control & Prevention (CDC) recently relaxed their COVID-19 guidelines, allowing fully vaccinated people to forego masks outside. But there are still settings where wearing your mask is crucial.

“The CDC says people who are fully vaccinated can go outside without a mask, but the important caveat here is ‘except in certain crowded settings and venues,'" senior study author Martha M. Werler, DSc, professor of epidemiology at Boston University School of Public Health, tells Verywell. "Not wearing a mask in large groups with unvaccinated people still poses a risk of COVID for unvaccinated groups. Vaccinated persons can carry and spread the virus."

She finds that mask-wearing is still the best course of action for mixed-vaccination status gatherings. “Even at small gatherings with unvaccinated people from different ‘bubbles,’ like graduation parties with relatives from afar and families from the neighborhood, all attendees should wear masks," she says.

To reduce the rate of COVID-19 cases nationwide, Werler says people need to wear their masks. "It’s that simple.”

Wearing Masks Led to Fewer COVID Cases

Werler and her team used the COVID-19 U.S. State Policy Database to collect policy and demographic data from all 50 states and the District of Columbia. They looked at data from April to October 2020.

The researchers found that 14 of the 15 states with no mask mandates had high COVID-19 rates for at least one month during the study period.

Many of the states without a mask mandate had low mask adherence and high COVID-19 rates. The opposite was true for states with mandates. However, Werler says her team did find substantial amounts of variation that could suggest other factors beyond mandates—such as political affiliation—could be at play. 

Only eight states reported that 75% or more people wore masks between June and September, leading to fewer COVID cases:

  • Arizona
  • Connecticut
  • Hawaii
  • Massachusetts
  • New York
  • Rhode Island
  • Vermont
  • Virginia

States with a 75% minimum mask adherence reported about 109.26 COVID-19 cases per 100,000 residents compared to the average of 249.99 per 100,000 residents in states with low mask adherence.

According to Werler, Arizona’s data was unexpected. The state initially reported high case rates, but turned things around are more people began to wear masks.

"Arizona surprised me because they went from having the second-lowest mask adherence in May and June [less than 22%] to the highest level in July and August [greater than 80%]. That’s a huge swing,” Werler says. “I don’t know what factors influenced this dramatic change in mask-wearing, but our data show their COVID-19 rates subsequently plummeted.”

When mask adherence dropped in September, COVID-19 cases increased in October. However, the COVID-19 rates continued to be higher in places with low mask adherence. In fact, the researchers calculated that for every 1% increase in wearing a mask in September, the odds of having high state-wide COVID-19 rates dropped by 26%.

What This Means For You

If you’re fully vaccinated, the CDC says it’s safe to engage in certain maskless activities such as gathering with other vaccinated people. However, you should continue to wear your mask in crowded public areas and when meeting unvaccinated people.

Are Mask Mandates Still Necessary?

"Lifting of mask mandates across the board without consideration of the caveats does open the opportunity for another wave," Werler says. "Large indoor gatherings without masking among a mix of vaccinated and unvaccinated persons is a recipe for trouble."

Research suggests that mandatory mask-wearing policies correlated with a lower number of COVID-19 infections and deaths. Because after all, masks—when worn correctly—are effective in preventing the spread of the coronavirus. Masks prevent you from inhaling or exhaling viral droplets that can linger in the air.

The three COVID-19 vaccines authorized by the FDA are also helping slow COVID-19 rates, allowing for the easing of restrictions. But with variants of concern circulating around the world, masking remains important—even as the public battles mask fatigue.

For now, relaxing some mask guidelines while staying vigilant is the government's compromise.

"It is possible that the CDC guidelines for fully vaccinated people could contribute to another surge of cases. [But] many of us are growing weary of mask-wearing and would love ‘permission’ to toss them aside and go back to pre-pandemic times," Werler says. "Unfortunately, the virus hasn’t gone away and is still easily transmissible. We all want to be able to be with friends and family this spring and summer, and we all don’t want to have [to] go back to the more stringent mitigation measures, so gathering outside and wearing masks is the best way to allow both to happen.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  1. Centers for Disease Control and Prevention. When You’ve Been Fully Vaccinated. Updated April 27, 2021.

  2. Brooks JT & Butler JC. 2021. Effectiveness of Mask Wearing to Control Community Spread of SARS-CoV-2. JAMA. 2021;325(10):998-999. doi:10.1001/jama.2021.1505