Face Shields Could Reduce User's Viral Exposure by 96% but they also have Downsides

Whether people should wear face masks to control the transmission of the coronavirus has been settled, and establishments are now requiring people to wear one when in public places. But as parts of the United States are slowly reopening, doctors want Americans to consider another layer of personal protective equipment to wear: clear plastic face shields.

Dr. Eli Perencevich, an infectious disease physician at the University of Iowa and the Iowa City Veterans Affairs Health Care System, said that he practices wearing a face shield every time he enters any establishment and even wears face masks, especially when the store requires it.

He and two other colleagues published an article last month at JAMA, about how clear plastic face shields could help reduce the transmission of infectious diseases when added to public health measures such as mass testing, contract tracing, social distancing, and hand hygiene.

Face Shields as Part of the New Norm

The New York Times reported that when schools start to reopen next month in Singapore, preschool students and teachers will receive face shields. Likewise, local health experts recommended teachers in Philadelphia to wear face shields when schools reopen, as what the teachers union in Palo Alto, California requested.

In hospitals, face shields have long been required equipment, especially for doctors and nurses in doing procedures such as intubating a COVID-19 patient and doing surgeries that may cause blood and bone fragments to fly out.

Dr. Sherry Yu, a dermatology resident, affiliated with Brigham and Women's Hospital in Boston, said that protecting the eyes and entire face from droplets that may carry the virus has become a bigger issue in health care settings.

People needed them to do nasal swabs, but as shortages loomed, Dr. Yu was among the many people and groups who begun making face shields for frontline healthcare workers.

"The nice thing about face shields is that they can be resterilized and cleaned by the user, so they're reusable indefinitely until some component breaks or cracks," Dr. Yu said. It can be disinfected using simple alcohol or rinse with soap and water to be contaminant-free again.

On the other hand, surgical masks and N95 masks are usually disposed after each use, although some studies have shown masks can be reused two to three times after being sterilized. Dr. Perencevich believes that face shields should be the preferred personal protective as it protects the entire face, including the eyes, and could prevent people from touching their faces.

Are Face Shields Effective in Protecting People from the Virus?

A cough simulation study in 2014 showed that a shield could reduce the viral exposure of a user by 96% when worn within 18 inches of someone coughing.

However, since most people are farther away from others when interacting, a face shield may not be necessary since large droplets that may contain the virus will quickly fall into the ground, said study lead author, William Lindsley, a Bioengineer at the National Institute for Occupational Safety and Health.

Moreover, there could also be instances when face shields are not as effective as an N95 mask in a close range, such as if a person faces sideways, or someone at the back coughs, or if someone standing coughs or sneezes while the person wearing the face shield is sitting.

There is also no research on how well face shields protect other people from the viral transmission. Saskia Popescu, a senior infection-prevention specialist at George Mason University, said that although she is a fan of face shields, she thinks that face shields can be swapped for face masks just yet.