What additional protection does one get from a face shield?

from Washington Post’s Coronavirus Update email of July 29, 2020

“What additional protection does a face shield provide if I’m also wearing a mask (e.g., on a plane)?” — Laura in D.C.

There hasn’t been much research on the benefits of face shields for the general public, but many experts believe they offer at least some protection against covid-19 when worn together with a face mask.

Let’s start with the skeptics. The Centers for Disease Control and Prevention flat-out “does not recommend use of face shields for normal everyday activities” — though the agency stops short of saying they have no benefit, and notes that some people “may choose to use a face shield when sustained close contact with other people is expected.”

Individual experts who have weighed in on the matter tend to be a bit more enthusiastic about face shields, noting that they can theoretically protect your eyes from droplets spewed by nearby people. “The only time a person would need to wear a face shield with a face mask is if you are in close proximity to people who are not wearing a mask at all, as the shield will help protect your eyes,” Hugh Cassiere, the director of critical care at Northwell Health’s North Shore University Hospital, told Fox News this week.

Nahid Bhadelia, the medical director of the Special Pathogens Unit at the Boston University School of Medicine, was even more upbeat about the idea of using one on an airplane. “The face shield is great if someone is sitting next to you and expelling on you,” she told The Post this month.

In fact, some airlines, such as Qatar Airways, require passengers and crew to wear face shields. And American Airlines recently allowed flight crew to wear them after a campaign by flight attendants, according to the Boston Globe.

Advocates for face shields assume that a sheet of plastic wrapped around your head can physically block infectious droplets from landing in a facial orifice — which is believed to be the main way the virus spreads. But until proper studies are conducted, it’s impossible to be sure they’re really helping. “It likely has a benefit. The benefit is not very well quantified,” Emily Sickbert-Bennett, the director of infection prevention at the University of North Carolina Medical Center, told The Post.

Face shields have been shown to offer some protection against other diseases, pre-pandemic, and they’re commonly used by medical professionals conducting risky procedures on contagious patients. Three infectious disease experts from the University of Iowa co-wrote an opinion essay in the Journal of the American Medical Association in April, advocating that shields be widely adopted. They noted that in simulations conducted before the pandemic, shields were shown to reduce exposure to the flu virus.

The Post interviewed one of those authors, Eli Perencevich, earlier this month. He cautioned that a shield won’t guarantee you’re protected from infection, but nevertheless recommended wearing one along with a mask the next time you fly.

“If you keep the face shield down, wear it, and wash your hands before taking it off and after taking it off — anytime you touch something — then you should be pretty reasonably protected,” he said.

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