By Melinda Wenner Moyer
Self, HEALTH, June 3, 2020
If you wear a face mask when you leave your home, you’re probably not doing it because you want to. Masks are awkward and uncomfortable, and they can be difficult to use correctly: If they aren’t applied and removed with clean hands, they can actually transmit infection rather than prevent it.
A growing number of researchers think there’s a better way. Face shields—which shield a person’s face with a clear curved plastic panel—are more comfortable, easier to put on and take off, reusable, and simple to clean. But most importantly, “we feel face shields are far more effective,” Eli Perencevich, M.D., a professor of internal medicine and epidemiology at the University of Iowa Carver College of Medicine, who in April published a commentary in JAMA in favor of face shields with two of his colleagues, tells SELF.
Research on face shields is limited but promising. In a 2014 Journal of Occupational and Environmental Hygiene study, researchers at the National Institute for Occupational Safety and Health placed a face shield on a breathing robot and had another robot 18 inches away “cough out” flu virus. The shield prevented the breathing robot from inhaling 96 percent of the virus within five minutes. In additional tests, the shield’s effectiveness varied based on the size of droplets expelled, but the overall indication was that shields can protect their wearers from other people’s germs.
No studies have yet addressed whether face shields protect other people from your germs, however, and this makes some scientists wary. “We don’t have the research to say that they will offer protection for those around you, should you be sick,” Saskia Popescu, Ph.D., an infection prevention epidemiologist at George Mason University, tells SELF.
But face shield proponents argue that based on the laws of physics, shields will likely protect others. Everything that flies out of your mouth is “going forward, and it’s hitting a giant piece of plastic,” Dr. Perencevich says. “It just physically can’t go through.”
Dr. Perencevich and others are now designing studies to help address this issue, but he says it’s difficult for research like this to get funded. “We’re more interested as a society in treatment than we are in prevention,” Michael Edmond, M.D., a hospital epidemiologist at the University of Iowa Carver College of Medicine, who co-authored the JAMA commentary with Dr. Perencevich, tells SELF. “There’s never money to do this kind of work. It’s never been prioritized.”
Some people are skeptical of shields because they are open on the sides and bottom. But these openings may not pose much of a problem. Research suggests that the coronavirus usually spreads via large droplets expelled out of a person’s mouth or nose, which are pulled down by gravity within a radius of six feet. (Hence the six-foot rule.) Shields prevent close-by expelled viruses from hitting another person’s face before they fall.
To get in through the shield’s openings, the virus would need to linger around in the air in smaller particles known as aerosols and eventually meander around the shield’s sides. But “the patterns of spread of [COVID-19] suggest that aerosol is unusual,” David Fisman, M.D., an infectious disease epidemiologist at the University of Toronto, tells SELF. Some studies have found that the virus can linger in the air, but epidemiological findings—such as surprising data suggesting that people often do not get sick even when other members of their household have the coronavirus—suggest that aerosol transmission is uncommon.
Still, for those who are concerned about the potential role of aerosols, or who might be at high-risk for complications from the coronavirus, one solution might be to wear shields and masks at the same time, suggests William Lindsley, Ph.D., a bioengineer with the National Institute for Occupational Safety and Health, who co-authored the 2014 robot coughing study. When robots wore both shields and masks in his study, the shields blocked 97 percent of the virus from landing on the masks, keeping them much cleaner.
It’s important to note, too, that research has not actually confirmed that cloth masks block a significant amount of virus from being expelled into the air. While cloth masks are thought to work best in terms of protecting others from droplets you expel (they don’t appear to protect you as well from other people’s germs), experts aren’t yet sure how effective they really are in that regard. “There haven’t been a lot of studies done on cloth masks,” Lindsley tells SELF.
The Centers for Disease Control and Prevention’s mask recommendations are based largely on research involving medical grade masks or N95 respirator masks, but those kinds of masks are very different from cloth masks. In a 2015 BMJ Open clinical trial, researchers found that health care workers who wore cloth masks over the course of four weeks were 13 times more likely to fall ill with respiratory infections compared with workers who wore medical masks. (3M, a company that produces medical masks, was the industry partner in the grant that funded this study. However, 3M did not have input on the study’s design, methodology, or analysis.)
Yet a small but oft-mentioned 2013 Disaster Medicine and Public Health Preparedness study suggests that even though medical masks would be better, cloth masks would have the potential to reduce spread of the influenza virus, which is a similar size to the coronavirus. More recently, a May 2020 opinion piece in the Annals of Internal Medicine examined decades of data on the subject, ultimately concluding that “although no direct evidence indicates that cloth masks are effective in reducing transmission of SARS-CoV-2, the evidence that they reduce contamination of air and surfaces is convincing and should suffice to inform policy decisions on their use in this pandemic pending further research.”
So cloth masks seem to be better than nothing—especially for reducing the spread of the coronavirus by people who have the disease but are asymptomatic and not isolating as they would if they had symptoms. And, currently, the CDC recommends that people wear cloth masks in public places where social distancing is difficult, because they’re easy to procure—medical masks are in short supply—and because less effective doesn’t mean ineffective.
Face masks “are not a bad recommendation,” Dr. Perencevich says. “It’s just that I think face shields are better.”
Shields also have many benefits that masks don’t. They protect not just your nose and mouth, but also your eyes; some research now suggests that when SARS-CoV-2 droplets hit the eye, they can then spread to infect the rest of the body. Also, unlike with masks, “you really can't wear them wrong,” Dr. Edmond says.
Shields prevent people from touching their faces, too, whereas masks can sometimes do the opposite. Additionally, shields can be reused after being washed with soap and water or wiped with disinfectant. They also allow people to see facial expressions and read lips, which is important for the millions of Americans who are deaf or hearing-impaired.
And while shields might look a little strange—they haven’t become a common sight yet in the U.S., even though they have become popular in Asia—they are far more comfortable than masks are and they allow for easier breathing. “You literally forget you have them on,” Dr. Perencevich says.
The upsides of the shields make them a cheap and easy way to protect one another,” Dr. Fisman says. In a set of policy and public health recommendations released in April 2020, the Infectious Diseases Society of America began recommending the use of face shields as a protective measure against the coronavirus, in addition to other methods such as masks.
Even if shields are found to have flaws with additional research—because of course, more research on them is essential—and even if only a fraction of people start wearing them, shields may still help quell disease transmission. The seasonal influenza vaccine is only 40 to 60 percent effective, but the CDC recommends it because it nevertheless saves thousands of lives. To stop the spread of the coronavirus, we only need to slow transmission such that each infected person infects less than one other person, on average, and “we don’t need a perfect intervention to do that,” Dr. Perencevich says. Face shields, he concludes, could be “a method that can save our economy and save lives.”