Are Face Shields a Better Option Than Face Masks for Protection From COVID-19?

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, MS1,2; Daniel J. Diekema, MD, MS2; Michael 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.

Screen Shot 2020-07-12 at 7.46.56 AM
Schematic of the experiment using particle spectrometers. The mouth of the cough aerosol simulator and the mouth of the breathing simulator were 152 cm (60 inches) above the floor and 46 cm (18 inches) or 183 cm (72 inches) apart. For experiments using influenza virus, the optical particle counters (OPCs) and the droplet size analyzer were not used, and a respirator was sealed to the breathing head form to act as a filter to collect the virus that was inhaled.

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.

John Murphy, MHSc PhD ROH CIH MACE | University of Toronto, Dalla Lana School of Public Health left a comment on the JAMA article which took exception to this crucial sentence about the 2014 face shield experiment:

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.people-wearing-diy-masks-3951628
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).

Does the Face Shield Cut the Mustard?

The idea of SARS-CoV-2 floating through the air in small particles and drifting around my face shield had made me uncomfortable with the face shield as sole protection in a medical office setting. I’d like some definitive evidence that  shed light on airborne transmission but alas there is none.

A July 13 JAMA VewPoint from three  Harvard physicians from Harvard’s “Department of Population Medicine ” entitled “Airborne Transmission of SARS-CoV-2:Theoretical Considerations and Available Evidence” summarized the current inconclusive evidence and concluded that shields or masks “should be adequate” to the task:

All told, current understanding about SARS-CoV-2 transmission is still limited. There are no perfect experimental data proving or disproving droplet vs aerosol-based transmission of SARS-CoV-2.

The balance of evidence, however, seems inconsistent with aerosol-based transmission of SARS-CoV-2 particularly in well-ventilated spaces. What this means in practice is that keeping 6-feet apart from other people and wearing medical masks, high-quality cloth masks, or face shields when it is not possible to be 6-feet apart (for both source control and respiratory protection) should be adequate to minimize the spread of SARS-CoV-2 (in addition to frequent hand hygiene, environmental cleaning, and optimizing indoor ventilation).

They end by saying:

It is perfectly understandable that many prefer to err on the side of caution, particularly in health care settings when caring for patients with suspected or confirmed COVID-19. However, the balance of currently available evidence suggests that long-range aerosol-based transmission is not the dominant mode of SARS-CoV-2 transmission.

Face Shields During Medical Office Visits

I emailed Dr. Perencevich on July 4 when I first started researching this topic and asked the following questions:

Are you still an advocate of the shield?
Do you think it is reasonable for me to wear only the face shield during my office visits? Obviously I would use more protection if there was a higher possibility of the patient being infected but our patients are screened prior to entering the exam room and should be low risk.
Are you aware of other authorities who feel as positive about the shield as you do.?

He kindly responded the same day:

My focus is on face shields in the community and not in healthcare. We use face shields and masks for all patient visits at this time.

So the major proponent of face shields in the community does not rely on them alone for his office patient encounters. Given the possibility of airborne transmission from an asymptomatic patient in the office I decided that a face shield alone would not cut the mustard.

I was still seeking relief from the mask constraints including fogging of glasses and facial irritation and I came up with a hybrid approach which was far more comfortable.

IMG_0292

I call this Pearson’s Face Shmask. The mask is a comfy cloth which is reusable and hangs loosely below my nose but covers my mouth through which I breathe. The shield is hospital-issued polycarbonate and extends below my neck and around to the side of my head. With this combination there is no fogging of the glasses and there is no touching of the face.

Obviously, data on the Shmask is limited at this point.

Keep in mind the following crucial points

-Let’s get every face covered

-The best face covering is the one you are most likely to wear

Faceshmaskingly Yours,

-ACP

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14 thoughts on “Are Face Shields a Better Option Than Face Masks for Protection From COVID-19?”

  1. If you’re looking for comfortable face masks, figs (the scrub company) has great ones. I have Trigeminal Neuralgia and can tolerate having them on my face most of the time.

    Reply
  2. The face shield may be a step up from masks, but I don’t think that is saying very much. Given that you can be fined upwards of $1000 for being seen in public without a mask (see D.C.), one would like to think that the evidence was strong and consistent. However, it is usually either indirectly addressing the question (as in the example above using robots and measuring droplet parameters), weak, or inconclusive. It certainly doesn’t justify the confidence I see and hear far too often. I’d like to know why studies like this do not get addressed publicly, as it much more directly answers the question about the efficacy of masks reducing respiratory viral illnesses and is very current: https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

    For those who are in favor of public mask mandates, I would like to know if this makes you question how firm your belief is in requiring something on pain of penalty, given that this is a systematic review of 14 RCTs addressing masks in nonhealthcare settings during 3 different influenza pandemics.

    In short: these studies found no effect at preventing disease spread.

    Dr. AnthonyP, I’m only writing this because I respect you and the insight you have given me through your website here. I have integrated some of your information into my own practice (FM) and have referred my residents to this website on multiple occasions and will continue to do so. I hope that this does not come across as an attack at you, but just a collegial challenge to a position you hold with which I don’t fully agree, nor fully disagree. In any event, thank you for your work and keep it up.

    Anthony

    PS: I’d take the face shield over the face mask if forced to make a decision. The facial expressions muted by the face masks are a big negative during patient visits and all other interactions in public life at the moment.

    Reply
  3. Thank you for the article and all of your information.

    The 2014 Study contains a confusing statement – “…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, …”

    Without studying the article for potential clarification, this is another way of saying the shields did nothing that 6 foot distancing won’t do alone (for inhaled virus)

    Reply
  4. Your photo was very helpful, as were your comments about the protection given to the wearer of Face Shields. Thank you.

    It seems there are two types of face masks – the first is to protect others if you are contagious, and are typically multi-use cloth masks. These are the most common mask, but give the wearer little protection.

    The second type of mask is designed to protect you from others, and is designated P95. P95 may be a single use mask, and are in short supply in Australia.

    Woodwork masks designated P2 are equivalent to P95, and are a good fallback if P95 is not available, with 3M being the most reliable brand.

    Face Shields seem a combination of both functions, protection for both wearer and others. Combined with a mask it is a belt and braces combination.

    Yesterday I was in the hardware store, keeping my social distancing. A passerby suddenly changed direction towards me, and shouted to his wife. I was contaminated by his breath – singing has been shown to spread COVID, so shouting would have the same effect. I have now decided to wear some protection when shopping – good decision but lousy timing, as the horse has bolted.

    Thank you for this Face Shield information- I will get one ASAP, and one for my wife. She is off to church this morning, with a P95 mask, and plans to sit to one side so as to avoid the breath of other singers. The chairs are placed 2 m apart so social distancing observed.
    .

    Reply
  5. My Internist wife wears one of these shields at work every day, but she is on the front line of COVID. She does freak out our six year old daughter when she wears it. You might enjoy this article by our friend John Ioannidis:

    https://www.medscape.com/viewarticle/933977?nlid=136436_4961&src=WNL_mdplsnews_200717_mscpedit_card&uac=13010HX&spon=2&impID=2464632&faf=1

    John was number 1 in his medical school class and my wife Irene was number 2. John is one of the most cited scientists in the world so when he talks it pays to listen.

    Reply
    • Thanks to Dr William Wilson for pointing us to the John Ioannidis interview. This is the kind of data-driven, reflective dialogue that we most need at this time.

      Reply
  6. When I return to my (dental) office after my recovery from my broken shoulder, I will wear a respirator or mask with shield. A psychiatrist friend is convinced he caught COVID while grocery shopping via eye exposure.
    On a slightly different subject, I was surprised at the graphic on the front page of today’s NY Times that showed that many European countries (not Spain or Italy of course, but Scandinavia) with lower levels of mask wearing than the U.S.
    (Scroll down 1/3 way down the page):
    https://www.nytimes.com/interactive/2020/07/17/upshot/coronavirus-face-mask-map.html

    Reply
    • Steven,
      Sorry about the shoulder. During my recent dental experience I felt pretty safe as everyone was wearing gowns, shields, masks, gloves and being extremely careful. I skimmed that NYT graphic and headline and was also surprised. As time permits I’m going to click on my county and see what the percentage is.

      Reply
    • Karen,
      Frankly I haven’t evaluated any commercial shields and I’m using one St. Lukes issued to me when I requested it.
      I do note some of Zshields are open at the top and I think the Perencevich article specifically talks about sealing between the top and the forehead.
      The medical type shields are attaching at the forehead.

      Reply

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