Face Shields May Be More Effective Than Cloth Masks in Protecting Against Viral Infection
Are face shields poised to replace — or augment — face masks throughout the community? Many medical experts say yes, pointing to both the benefits of face shields and the shortcomings of cloth face masks.
In April, the CDC recommended the public use of cloth face coverings, in addition to social distancing, to protect against the transmission of COVID-19. In places like Los Angeles, face coverings are now mandatory to enter essential businesses such as grocery stores.
Since the limited supply of N95 masks has made it difficult for non-essential workers to obtain medical-grade face coverings, the majority of the public have turned to cloth face masks, which are frequently made at home.
And with shortages of PPE, some healthcare workers who don’t have access to N95 masks are relying on surgical masks when treating patients. As Infection Control Today reports, “surgical masks offer little protection to healthcare workers,” and are not an adequate alternative to N95 masks.
Many, including Dr. James Cherry, a UCLA infectious disease expert, now think that face shields are more effective than masks when it comes to protecting the person wearing the PPE from viral infection.
It’s widely agreed that a face mask does more to protect others than the person wearing it. A face shield, on the other hand, may offer the wearer additional protection — and may be more effective in preventing viral transmission.
In a report in the April 29 Journal of the American Medical Association, medical experts led by Dr. Eli Perencevich state that, “Cloth masks have been shown to be less effective than medical masks for prevention of communicable respiratory illnesses … Face shields may provide a better option.”
While it’s too early for evidence supporting the effectiveness of face shields against COVID-19 specifically, there have been promising studies with influenza. According to the JAMA report, “Face shields appear to significantly reduce the amount of inhalation exposure to influenza virus, another droplet-spread respiratory virus.”
In a simulation study referenced in the same report, face shields reduced immediate viral exposure by 96% when worn by a simulated health care worker within 18 inches of a cough.
“That’s only with one face shield—a face shield on the receiver end,” said Dr. Michael B. Edmond, one of the authors of the JAMA report, in an interview with Contagion Live. “But if everybody is in face shields, you have both source control and protection of the susceptible person, and so we would envision that the effectiveness would even be better in that situation.”
One of the most obvious advantages of face shields is that they cover the eyes, in addition to both the nose and the mouth. Face masks, on the other hand, leave the eyes exposed.
Coronavirus can be transmitted through the eyes if, for example, an infected individual coughs near someone, or a person who comes into contact with the virus rubs their eyes. Face shields prevent infected droplets from reaching the eyes, which is why health care professionals treating coronavirus generally cover their eyes with either a face shield or goggles.
Some experts worry that cloth face masks are not washed as frequently as they should be, and when they are, the cloth can deteriorate to allow more particles through the covering. Because cloth masks degrade over time, they are not designed to last for an extended period.
Face shields, on the other hand, are made of durable plastic that can better withstand the test of time. Many face shields are also reusable, and can easily be washed with soap and water or a non-abrasive disinfectant between uses.
Communication and Visibility
It can be difficult to communicate while wearing a face mask, which leads many people to pull the mask down when speaking. With a face shield, there’s less of a visual barrier, which makes it easier to read lip movements, and allows facial expressions to be seen. This can be especially important with difficult conversations in a medical setting.
In his interview with Contagion Live, Dr. Edmond explains, “My wife, who’s an oncologist, talks about how difficult it is to have important conversations with patients about prognosis or end of life when you’re wearing a face mask where it is a barrier to communication. I think the face shield is a little easier from that standpoint, definitely.”
The Comfort Factor
In an interview with the L.A. Times, Dr. Cherry stresses that one of the biggest issues with cloth face coverings is that they can be itchy and uncomfortable, which can cause people to touch their face more in order to adjust the mask.
The problem, of course, is that people can easily infect themselves if their hands have come into contact with the coronavirus and they touch their nose, eyes or mouth. Likewise, if someone wearing a mask who is infected touches their face, they risk spreading their own infected secretions to others when they touch various surfaces.
A Barrier Against Face Touching
A face shield is a good reminder not to touch your face, even if you forget. If someone wearing a face mask goes to itch their nose or rub their eye, they’ll simply hit a plastic barrier that stops them from touching their face. And since face shields tend to be more comfortable and less restrictive than face masks, there should be a lot less temptation to make adjustments that can lead to face touching.
What About Aerosols?
Currently, evidence suggests that coronavirus is primarily transmitted through droplets, rather than aerosols. And while Dr. Edmond recognizes that face shields may not be quite as effective if there’s aerosol transmission, he tells Contagion Live:
“We think by having both the susceptible person and the infectious source in face shields, even that aerolization will be markedly decreased, and there’s nothing to prevent people from putting a mask on underneath the face shield if they want to do that.”
Prioritizing PPE for Front-Line Workers
Dr. Edmond and his colleagues believe that if everyone wears a face shield, the transmission of the virus would go down, which could help speed up the re-opening of society. Of course, the availability of face shields (like other PPE) remains a challenge, and the priority should go to healthcare professionals and other essential workers who are on the front lines.
Whether or not the general public widely adopts face shields remains to be seen. In the meantime, Jackson Medical is proud to offer standalone, single-use medical face shields for hospital workers, dental and medical offices, and others with a pressing need for personal protective equipment.