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While enjoying my early morning bowl of sugar-laden breakfast cereal, some CNN, and a few minutes of peace and quiet earlier this week, I watched a commercial for a new brand of face shields. ZShield, a trademarked line of face shields manufactured by ZVerse, comes with claims of providing protection from the spread of COVID-19 by way of an innovative design that is more comfortable and user friendly. Their website further claims that the benefit of a ZShield goes beyond lowering the wearer’s risk:

By wearing one of our ZShields, you are helping to shield yourself and those around you, your neighbors, customers, nurses and doctors, grocery store clerks, teachers, hair stylists, restaurant servers and so many others. We invite you to join us and Be the Shield.

With one exception, the face shield specifically marketed for medical professionals (ZShield Health), the design of the various ZShield products involves a unique attachment at the neck and a shield that goes up rather than down. In addition to this feature, these shields can easily be pulled down when protection from respiratory viruses is less desirable, such as when drinking coffee at your favorite cafe. The commercial and website heavily feature a face shield designed for children attending school, and it is implied that a face mask is rendered unnecessary by wearing the ZShield Youth or one of the other shields.

It all sounds so amazing. It’s comfortable, easy to use, even dishwasher safe. And according to ZShield, not everyone can wear a mask all day, so this must be a great alternative. Plus the learning environment for our children is more positive because facial expression is an important aspect of communication. It almost sounds too good to be true.

ZShield: It’s too good to be true

There are a lot of problems with these products, and a lot of red flags on the website promoting them. Because I’m the pediatrician on the team, however, I’ll try to mostly stay in my lane and focus on their use by children as personal protective equipment. But honestly, the issues I’ll raise with using ZShield to prevent COVID-19 in kids are pretty generalizable.

So are these face shields effective? The website FAQ provides one of the worst examples of marketing malarkey that I’ve seen in quite a while:

Are your face shields effective in preventing the spread of COVID-19?

Our ZShield Flex and ZShield Wrap face shields provide a barrier for respiratory droplets. Our face shields are designed based on customer feedback and demand for a comfortable, reusable, easy to clean face covering that provides a threshold of hygiene while allowing for easy communication and a full view of the wearer’s face.

Customer satisfaction is probably not the best primary metric when designing a medical device aimed at the prevention of an infectious disease. I mean, it is true that an effective product that nobody will use is worthless. But so is something that everyone will wear but doesn’t provide much protection. Where will ZShield fall on this spectrum? Hmmm…I wonder.

Oh, and what the heck is a “threshold of hygiene”? Rubbing your hands with dry bar soap provides a threshold of hygiene. So does 1-ply commercial toilet paper for that matter, but I would not consider either of these interventions to be effective. I need a bit more detail when I’m facing a viral pathogen that might put me or my family on a ventilator.

This answer above also doesn’t mention the ZShield Youth or the ZShield Health, probably because a lawyer(s) told them not to include those for, let’s just say legal reasons. I do, however, have a few more problems with this answer other than just the strategic bait and switch. First off, the claim that these products “provide a barrier for respiratory droplets” is true but problematic. Just how protective a barrier is against the novel coronavirus depends on the design of the barrier.

The best “barrier”, of course, is distance from the virus, ideally enhanced by vaccine induced herd immunity. Face masks also provide an excellent barrier that is the next best thing to widespread immunity. Classic face shields that start at the forehead, go down far enough to cover the face, and wrap around the side of the head provide a helpful barrier, but not to the same degree as masks. And there is solid evidence that a combination of a mask and face/eye shielding increases protection.

But what about the innovative design of the ZShield products? Does it work as a mask substitute? Does it work as well as classic face shields? I mean, it has to at least be better than nothing?

ZShield: Probably worse than nothing?

The unique design of up-going ZShield face shields is bad. It’s comically bad. It’s like I’ve been fooled by a very effective, Poe’s-Law-defining, satirical performance art piece. But I haven’t been, because it isn’t satire. It’s real.

There are four fundamental forces in physics that govern how all objects and particles interact. The sexiest is gravity, coming in just ahead of the strong interaction. Respiratory droplets that are > 5 micrometers in diameter, once expelled from their source (probably Larry in accounting), are quickly pulled towards the center of the Earth by the gravitational force. See where I’m going with this yet?

If a person is wearing a face shield that is open at the top, as all ZShield products except for the one marketed to healthcare professionals are, they are within roughly 3 feet of the source, and their head is situated below said source, their face shield will inconveniently collect falling infected respiratory droplets and direct them towards the eyes, mouth, and nose. Children, in general, live for many years below most adults.

Yet the ZShield website FAQ provides the following reassuring information:

According to an article published in JAMA, 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.

The article they cite, which does concludes that face shields should play a role in reducing the transmission of the novel coronavirus, cites a study that involved the use of coughing patient and breathing worker simulators. In addition to the fact that it involved a different virus, the most glaring problem with using the study as support for ZShield products is that the authors tested classic face shields that attach at the forehead, with no gap between the shield and the skin, and that extended down to the chin, just like the CDC recommends. There have been a grand total of zero studies looking at face shields that attach at the neck and open to the sky, and there probably never should be.

Also left out of the above answer is the fact that the study looked at short term exposures to simulated coughs at 1 and 30 minutes. This is not generalizable to many situations, especially adults at work, or kids in school, both in indoor environments for hours at a time. The 96% reduction of inhaled particles was seen in the immediate period after a cough involving large droplets but there was only a 68% reduction of immediate inhalation of smaller airborne particles.

At 30 minutes, there was only a 23% reduction of inhaled smaller airborne droplet nuclei. This is important because there is growing evidence that SARS-CoV-2 is also spread via airborne particles smaller than 5 microns that can float further and for a much longer period of time. And, again, this study did not include face shields with the unique ZShield design. It did confirm that distance from the source of droplet or airborne particles is an extremely important factor in lowering your risk of infection. For all but the very tall, keeping at a distance from people is probably more effective at avoiding illness from the novel coronavirus than wearing a ZShield with the neck attachment and getting within 6 feet of an infected individual.

Theoretically, if a child or shorter adult were to cough directly up into someone’s face at an extremely close range, one of these unique ZShield face shields might actually provide better protection than a classic face shield. It would depend on how much force was generated though because any droplets that were forced above the head of the ZShield wearer would quickly settle right into their various face holes.

But at least the FDA approval process for these is on the level…right?

ZShield: Yeah…it’s probably not on the level

With so many obvious problems with the design of the ZShield face shields being marketed to the general public, it’s hard to imagine that they would be approved by the FDA for use. Well, though they probably don’t deserve to be, they might barely make the grade, but only after a relaxation of the approval process during the pandemic.

In April, the FDA issued an emergency use authorization that included face shields because of widespread PPE shortages in healthcare settings, making the process extremely simple. Face shields were declared to be exempt from premarket approval and, when marketed for use only in healthcare settings, needed only follow a few general guidelines. They had to be labelled properly (single use, reusable, etc.), not have an attached mask component, not burst into flames spontaneously, and cover the front and sides of the face.

There is no specific mention of which direction they should point in the FDA emergency use authorization, however it does state that they must be used in accordance with CDC recommendations. These recommendations do specify that a face shield should cover the forehead. Only the ZShield Health, the first face shield they produced and one that is only marketed to healthcare entities, follows this guideline because it is designed like a classic face shield.

In May, the FDA issued updated guidance that superseded the April emergency use authorization. This time, they included distribution of face shields intended for medical use to the general public and softened the approval criteria by taking out the clear need to adhere to CDC recommendations for face shield design. They also altered the wording regarding undue risk just a bit. Here is the original:

The product is not intended for any use that would create an undue risk in light of the public health emergency; for example, the labeling does not state that use of the authorized face shield alone will prevent infection from microbes or viruses…

Not surprisingly, ZVerse began marketing the new ZShield products to the general public that same month. In the press releases, they straight up claim that their unique face shields can serve as an alternative to face masks, which is demonstrably untrue. In the FDA update, the language about proper labeling and lack of flammability was the same. But they took out the part about proscribing labeling that claims that face shield use alone is effective as a prevention of infections and replaced it thusly:

The product is not intended for any use that would create an undue risk in light of the public health emergency, for example, the labeling does not include uses for antimicrobial or antiviral protection or related uses or uses for infection prevention or reduction or related uses…

When you look at the product labels for the ZShield products, sure enough they don’t make any claim about preventing infections. Yet as I’ve already described above, that kind of language is all over the marketing, which is pretty shady in my humble opinion, particularly given how bad their design is. If this isn’t undue risk in light of the public health emergency we are experiencing during this pandemic, I don’t know what is. It’s unfortunate that there is nothing in the language of the FDA approval guidance that would require additional protections when such a significant change is made to the form of an existing medical device.

Conclusion: ZShield is not the answer

The manufacturers of ZShield appear to be choosing comfort and ease of use/customer preference over effectiveness in the design of products that they are selling to the general public. It’s dangerous to promote what is essentially an untested medical device with such low likelihood of preventing the spread of COVID-19. And the degree to which they’ve contorted the available scientific studies and expert recommendations to give the appearance of legitimate protection is wrong.

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Posted by Clay Jones

Clay Jones, M.D. is a pediatrician and a regular contributor to the Science-Based Medicine blog. He primarily cares for healthy newborns and hospitalized children, and devotes his full time to educating pediatric residents and medical students. Dr. Jones first became aware of and interested in the incursion of pseudoscience into his chosen profession while completing his pediatric residency at Vanderbilt Children’s Hospital a decade ago. He has since focused his efforts on teaching the application of critical thinking and scientific skepticism to the practice of pediatric medicine. Dr. Jones has no conflicts of interest to disclose and no ties to the pharmaceutical industry. He can be found on Twitter as @SBMPediatrics and is the co-host of The Prism Podcast with fellow SBM contributor Grant Ritchey. The comments expressed by Dr. Jones are his own and do not represent the views or opinions of Newton-Wellesley Hospital or its administration.