• A new review of mask studies is generating buzz about whether masks work to prevent COVID.
• The review doesn't draw any major conclusions — but people are using it to say mask mandates failed.
• Mask studies have become a Rorschach test that people use to validate preexisting beliefs. 

Masks. They're annoying. They're partisan. They're passé. 

And do they even work to keep people healthy?

A new review of mask studies by the prestigious Cochrane Collaboration suggests they only perform so-so.

The review caused a media frenzy about the face coverings that have been such a central and political feature of our lives for the past three years.

In fact, even some of the researchers performing the review took this lackluster finding as a ringing indictment of COVID-era mask mandates. 

"There's no evidence that they do work." Tom Jefferson, a University of Oxford tutor who co-authored the review, said in a recent interview. 

That's not strictly true. We have a lot of evidence about what masks can and can't do — and this new review has been taken wildly out of context.

The new review looked at 78 research papers — but most weren't about COVID

This new research roundup, out January 30, is the latest update to a 16-year-old Cochrane Systematic Review designed to assess whether "physical interventions" — including masking and handwashing — help limit the spread of respiratory viruses.

Cochrane is one of medicine's rock star publications — designed only to evaluate the most up-to-date, well-designed trials, with the ultimate goal of promoting better evidence-based decision making in healthcare. But the researchers didn't actually draw firm conclusions about whether masks work or not.  

"We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses," the authors wrote. "The results might change when further evidence becomes available." 

There were 15 years of different studies included in this mega review of 78 research papers — six pertained to COVID, but many more were about flu. Some covered masks, while others assessed the impact of handwashing and gargling on disease transmission. 

Perhaps most importantly, several mask studies included in the new review didn't require anyone to actually wear a mask — rather, researchers just handed masks out to some people, and not others, to see if disease rates were better when masks were available (they were.)

The review left out real-world examples of masks working 

There were also some important COVID-era mask studies that weren't included in this review because, even though they were well-designed, they weren't randomized-controlled trials — which some consider to be the gold-standard in medicine. 

But these studies are also instructive.

Take the two COVID-positive Missouri hairstylists who coiffed 139 clients. All wore masks; no one got sick. Or the COVID outbreak aboard the USS Theodore Roosevelt, where the masked medical personnel suffered fewer cases. And many studies of large school districts across the US – from Georgia to Massachusetts, show that where masks are worn, COVID case rates are consistently around 30-40% lower.

We have decades of evidence showing masks can block out viruses

Physically speaking, we know masks and respirators can work well to prevent bad stuff from entering people's noses and mouths — whether the threat is a virus, smoke from a fire, coal dust, or mold spores. 

High-quality masks have already been used for decades to help mitigate — but not entirely prevent — the spread of highly-infectious pathogens including measles and tuberculosis. 

During the pandemic, lab workers at the Centers for Disease Control and Prevention (CDC) double-masked dummies with surgical and cloth masks and discovered that strategy reduced COVID transmission from one face to another by up to 96.4%. 

"There are inviolable laws of nature that we can rely on," Linsey Marr, an aerosol scientist at Virginia Tech who studies how viruses move through the air, told Insider. "Filtration of particles by masks is a physical process that has laws."

The real problem with masks is you

When worn diligently by individuals, masks can be a good tool for blocking viruses. 

But they're not a silver bullet. And, let's be honest: no one can wear their mask all the time.

Healthcare workers take their masks off to eat in break rooms, where COVID spreads from coworker to coworker. Friends and family gather for intimate events including funerals and birthdays, where closeness is important. 

"Even the most conscientious person," said Dr. Don Milton, an infectious disease researcher at the University of Maryland, "is going to have some failures" when it comes to wearing their mask.

One huge study included in the review looked at masks in a real-world setting: in villages across Bangladesh comprising more than 300,000 people. Some wore masks, and some didn't. The villages with the most diligent mask-use saw reductions in COVID of about 12%. 

The study authors insist that's something to celebrate. "We didn't get 100% of people wearing masks — we got 40%," one of the Bangladesh study authors, Ashley Styczynski, previously told Insider. "It wasn't everybody. And yet, we still were able to measure an effect."

At the end of the day: Don't trust anyone with a simple assessment of masks

Think of masks like condoms for your face. They're tools that can be used to prevent infection. But they're not going to prevent outbreaks, or even curb them, all on their own. 

In fact, in 2014, Cochrane published a similar systematic review on condoms. They found that programs promoting condom use didn't have a significant impact on HIV transmission, but this wasn't taken as evidence that condoms "don't work." The authors endorsed these programs to improve people's knowledge of STDs — even though they won't force everyone to put a condom on every time they have sex. 

In other words, condoms, like masks, should be but one part of disease prevention efforts. 

In March of 2020, we wrote about how face masks weren't a perfect solution to the spread of the novel coronavirus. In two years, lots of new studies have been done, and the same advice still holds.

Any pundit or scientist trying to give you a clear answer about whether masks definitely work — or fail — in the face of complicated, thorny, and nuanced evidence, should be treated with the utmost skepticism.

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