Face Masks vs Face Shields: A commentary on their use during COVID-19

By: Kandi Grimes

During this unusual time of the COVID-19 pandemic, states, cities, districts, and schools faced questions about how and when schools would return to in-person instruction in the Fall of 2020. Online learning, hybrid learning (a combination of online and in-person), or complete on-campus instruction have been implemented in many states to answer these questions.  Concerns surrounding the risks of opening schools loomed over those participating in the process. Precautions were taken and, as noted in various articles on the subject, “schools are not islands”, so it was very likely that when in-person school resumed, coronavirus cases would follow. Among states reporting coronavirus cases, Texas counted 700 among public school districts and charter schools as of 9/20/2020.

Safety protocols provided by the U.S. Centers for Disease Control and Prevention (CDC) prior to school openings have remained in place. The agency has stated, though, that regardless of current risk indicators, it is critical to ensure the use and layering of mitigation strategies:

  • Use of masks
  • Social Distancing (six feet to the extent possible)
  • Cleaning and disinfection
  • Cohorting
  • Adequate hygiene supplies
  • Physical barriers/guides when social distancing is limited
  • Hand hygiene and respiratory etiquette
  • Limit nonessential visitors
  • Contact Tracing
  • Staying home when appropriate
  • Staggered scheduling

The CDC has recommended that all school employees wear cloth face coverings and many district and school leaders incorporated that guidance into their reopening plans. The use of masks is still considered to be a large deterrent in spreading the coronavirus. Some states have opted to provide face masks for teachers and staff to help prevent transmission of the virus when an infected person coughs, sneezes, or talks while social distancing at least 6 feet apart. For example, to assist in the implementation of his executive order requiring the use of face masks in schools, Texas Governor Greg Abbott has indicated that the state will continue to purchase and distribute PPE to schools at no cost to the school districts. The Texas Education Agency (TEA) concurrently presented their guidelines for schools and has since updated their posting. Dr. Ruth Berggren, an infectious disease specialist at the UT Health San Antonio’s Long School of Medicine, has noted that the guidelines listed by the TEA can be enough to keep children safe in the classroom.

Whether in or out of the classroom the CDC recommends the following when selecting or wearing a mask:

  • Be sure to wash your hands before putting on a mask
  • Do NOT touch the mask when wearing it
  • Wear masks with two or more layers
  • Wear the mask over your nose and mouth and secure it under your chin
  • Wear a mask that fits snugly against the sides of your face
  • Masks should be worn by people two years and older
  • Masks should NOT be worn by children younger than two, people who have trouble breathing, or people who cannot remove the mask without assistance
  • Do NOT wear masks intended for healthcare workers, for example, N95 respirators
  • The CDC does not recommend the use of neck gaiters, bandanas, masks with exhalation valves or vents, or face shields alone. Evaluation of these face covers is on-going but effectiveness is unknown at this time

The risk for infection is highly dependent on distance to the individual infected and the type of face mask and eye protection worn.[1] The three types of facial protection include:

  • N95 – Prevents inhalation of 95% of 0.3 µm particles
  • Surgical mask – Filtration of all air reaching the mouth and nose is required for particles ≥5 µm
  • Face shield – Provides barrier protection from splash and splatter contamination, as well as acutely expelled aerosols.[2] However, the evidence for the effectiveness of face shields in preventing transmission of viral respiratory diseases is minimal, as highlighted in a recent narrative review.[3]

The use of face masks continues to be an important element of prevention for the entire nation.  Masks vs. face shields, however, remains a popular question. Although face masks are recommended by the CDC, they do not benefit everyone.  In some cases, a teacher, student, or employee in any profession may need to wear a face shield in lieu of a mask. Various reasons for the use of a face shield include employee physical and mental health considerations and teachers instructing a language class or a class that contains students with intellectual and developmental disabilities. The CDC does recognize that there are specific instances when wearing a cloth face covering may not be feasible, and it is suggested that a consideration for adaptations and alternatives be allowed whenever possible. Since this pandemic has continued for longer than some anticipated, circumstances surrounding one’s reason for a wearing mask or a shield may change.  It is nice to have the option to choose, if necessary.

The CDC considers face shields as primarily used for eye protection for the person wearing it. At this time, it is not known what level of protection a face shield provides to people nearby from the spray of respiratory droplets from the wearer. There is currently not enough evidence to

support the effectiveness of face shields for source control. Therefore, the agency does not currently recommend the use of face shields as a substitute for masks. Using cough simulation, researchers demonstrated that face shields were shown to reduce the risk of inhalation exposure up to 95% immediately following aerosol production. However, protection was decreased with smaller aerosol particles and 30 min after cough simulation, due to persistence of airborne particles and particle flow around the sides of the mask.[4]

In Texas, however, the TEA has noted that full-face shields may be used in place of a mask to protect eyes, nose, and mouth whenever a mask is not feasible or whenever the education context may benefit from the ability to see an individual’s full face. Dr. Fred Campbell, UT Health San Antonio physician, mentioned in his interview with the Texas Public Radio program, Texas Standard, regarding the use of masks and face shields, “There are masks that are now available – there’s one called the Hello Mask – that is made of the component over the mouth and nose area that is transparent and allows the mouth to be visualized,” Campbell said. “So that would be an alternative to a face shield, which appears to be effective and filtering as well.”

Some advantages of face shields compared to other forms of face/eye protection are:

  • relatively inexpensive
  • can be worn concurrent to other face/eye PPE
  • no impact on vocalization
  • do not impede facial nonverbal communication

The CDC has noted that face shields are the least effective protection against Covid-19. They are however better than no protection.  An epidemiological study[5] reported that the nonuse of face shields by nurses, during high-risk aerosolizing procedures on patients with respiratory infections, resulted in a greater than three-fold increased risk of infection.

There is currently no universal standard for face/eye protection from biological hazards.[6] There are also no interventions that are associated with complete protection from infection. These unprecedented times come with recommendations, restrictions, and duties that are all in addition to the typical norms of the school year for teachers, students, and staff. Hopefully, they will find some solace in the fact that the CDC as well as most states are continuously re-evaluating and updating protocols for their safety.  Additional preventative measures are being explored across the United States. UT Health San Antonio is included in this endeavor. Wearing a mask or a face shield in a school setting or for a different profession is a small price to pay, I believe, for protecting ourselves and our fellow man. We are all in this together!

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