The skeptical cardiologist fully endorses public health recommendations (and in some cases mandates) to wear face coverings to reduce the spread of COVID-19.
In response to an alarming rise of COVID-19 cases after easing of restrictions in his state, even Texas governor Gov. Greg Abbott issued a statewide mask mandate on July 2.. First-time violators will be issued a warning, though repeat offenders could be fined up to $250.
Texans living in counties with more than 20 coronavirus cases must wear a face covering over the nose and mouth while in a business or other building open to the public, as well as outdoor public spaces, whenever social distancing is not possible.
The Texan mandate provides exceptions for children under age 10 , people who have a medical condition that prevents them from wearing a mask, people who are eating or drinking, and people who are exercising outdoors.
Although I don’t have any lung condition that would prevent me from wearing a mask, due to a skin condition that affects my cheeks I find wearing masks to be incredibly uncomfortable. One that makes prolonged wearing such as when seeing patients in the office a grueling experience.
Consequently, when I spotted an article entitled Moving Personal Protective Equipment Into the Community:Face Shields and Containment of COVID-19 my ears perked up.
Written by a trio of infectious disease expert at the University of Iowa (Eli N. Perencevich, MD, MS1,2Daniel J. Diekema, MD, MS2Michael B. Edmond, MD, MPH, MPA2) the JAMA Vewpoint posits that “face shields may provide a better option” than face masks for those in the community during COVID-19.
Arguments for the Efficacy of Face Shields
What factors make shields potentially a better option?
The authors feel availability of face shields is “currently greater than that of medical masks.” because “face shields require no special materials for fabrication and production lines can be repurposed fairly rapidly.”
They also note some practical advantages for shields over masks:
While medical masks have limited durability and little potential for reprocessing, face shields can be reused indefinitely and are easily cleaned with soap and water, or common household disinfectants. They are comfortable to wear, protect the portals of viral entry, and reduce the potential for autoinoculation by preventing the wearer from touching their face. People wearing medical masks often have to remove them to communicate with others around them; this is not necessary with face shields. The use of a face shield is also a reminder to maintain social distancing, but allows visibility of facial expressions and lip movements for speech perception.
As evidence for shields effectiveness the authors cite a 2014 Journal of Occupational and Environmental Hygiene study, in which 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 Viewpoint summarizes the relevant findings from that 2014 paper as follows:
Most important, face shields appear to significantly reduce the amount of inhalation exposure to influenza virus, another droplet-spread respiratory virus. In a simulation study, face shields were shown to reduce immediate viral exposure by 96% when worn by a simulated health care worker within 18 inches of a cough. Even after 30 minutes, the protective effect exceeded 80% and face shields blocked 68% of small particle aerosols, which are not thought to be a dominant mode of transmission of SARS-CoV-2. When the study was repeated at the currently recommended physical distancing distance of 6 feet, face shields reduced inhaled virus by 92%, similar to distancing alone, which reinforces the importance of physical distancing in preventing viral respiratory infections.
Does Airborn Transmission of Virus Circumvent The Shield?
This sounds quite promising for face shields but there is no consensus among public health experts that face shields are superior to cloth face coverings in the community.
Even after 30 minutes, the protective effect exceeded 80% and face shields blocked 68% of small particle aerosols, which are not thought to be a dominant mode of transmission of SARS-CoV-2.
Murphy’s comments stress that small particle aerosols indeed may be important:
Attenuation of large droplets by a face shield could only lessen community transmission if persons with COVID-19 expelled larger droplets exclusively. However, coughs and exhalation generate droplets mainly in range of <0.5 to 20 µm, which do not behave ballistically, meaning the large droplet protective value of face shields affords no protection from SARS-CoV-2 virions in coughs and breath. There is also growing evidence that inhalation of respirable droplets generated simply by exhalation that can circumvent a face shield may be a dominant mode of community transmission.
The issue of airborne transmission of SARS-CoV-2 has in the last two weeks sprung into the national news headlines,
Let’s Get Every Face Covered
The authors of the face shield JAMA article have been active on social media in defending their face shield proposal. A recent NY Times articles quotes Dr. Perencevich extensively and summarizes their viewpoint:
Dr. Perencevich and his colleagues expect that more research will show shields to be superior to cloth masks, not only because shields provide full face protection but as they are nearly impossible to wear incorrectly.
Dick Gordon, one of the coauthors of the JAMA viewpoint article writing on the health care blog Controversies in Hospital Infection Prevention defended his position:
Our recent JAMA viewpoint, Moving Personal Protective Equipment into the Communnity, in which we argue for universal face shields in the community settting, was written from a public health framework. This was perhaps not clear to the many individuals who pointed out that in some cases there could be airborne transmission of the virus for which a face shield may not work. Yes, we get that, but the epidemiology convinces us that the airborne route is a minor mechanism of transmission.The bottom line here is that we can’t let perfect be the enemy of the good. We recommend influenza vaccine every year despite an average seasonal effectiveness of approximately 40%. The best face covering is the face covering that people will wear. Though I personally favor face shields for community use, I am happy to see faces covered in almost any way possible (which is why I love the photo above).