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Why face shields alone won’t protect you from COVID-19, study says

Why face shields alone won’t protect you from COVID-19, study says
(Image credit: Getty)

If you just wear a plastic face shield without a mask underneath, you are not protected enough from the coronavirus, according to new research. The findings have arisen from a new study (opens in new tab) wherein researchers analyzed the risk of COVID-19 infection in medical workers who were exposed to a sneeze when wearing a face shield. The study was published earlier this month in the journal Physics of Fluid.

Researchers found that while plastic face shields may trap large droplets from a COVID-infected sneeze or cough on the outside of the shield, small droplets have been observed leaking through into the space between the face and the face shield. 

Known as 'vortex rings', these tiny droplets from infected sneezes and coughs can't be seen by the naked eye, yet they get inside the face shield in as little as 0.5 seconds after the start of the sneeze from an infected individual standing one meter away. Study co-author Dr Fujio Akagi, based at Fukuoka University, explained (opens in new tab) that, “If the arrival time is synchronized with inhalation, the shield wearer will inhale the droplets.”

Key highlights from the new study:

  • Droplets from infected sneezes are quickly transported by the high velocity airflow caused by sneezing itself AND by the vortex rings generated by sneezing.
  • Tiny droplets powered by these vortex rings can leak inside the face shield at the top and bottom edges.
  • While face shields alone are proving ineffective at 1) trapping the droplets of COVID-infected wearers and 2) protecting healthy wearers, they do work well when worn with a protective mask underneath.

Why face shields won’t protect you from COVID-19, plus the best face masks to wear: Sneeze flow during face shield coronavirus testing

(Image credit: Fujio Akagi, Isao Haraga, Shin-ichi Inage, Kozaburo Akiyoshi)

Types of protective masks includes reusable fabric face masks (opens in new tab), medical masks for over 60s and people with COVID or who live with someone who has it, and homemade face masks (opens in new tab). The type you need depends on the rate of virus transmission where you live, whether you're high risk, and whether you have been exposed to someone with COVID-19 or have symptoms suggestive of infection. 

The list of coronavirus symptoms (opens in new tab) includes a new cough, fatigue, loss of taste or smell, and a fever, which can be monitored using one of the best digital thermometers (opens in new tab)

Face shields alone are no match for a COVID-19 sneeze

Plastic visors are widely used by frontline workers in shops, restaurants, hospitals, salons and other people-facing businesses, but this new research argues that face shields aren't robust enough on their own to protect against airborne infection.

While the World Health Organization (opens in new tab) doesn’t currently consider COVID-19 to be a disease that can remain infectious for long periods of time while in the air, ongoing research into the disease by scientists is attempting to prove otherwise. A recent study (opens in new tab) in America showed that the coronavirus could be detected and isolated in the air as much as 4.8 meters away from an infected patient. 

Study source

'Effect of sneezing on the flow around a face shield' by Fujio Akagi, Isao Haraga, Shin-ichi Inage and Kozaburo Akiyoshi, December 8 2020, Physics of Fluids. DOI: 10.1063/5.0031150

With small droplets able to enter the gap between a person’s face and the face shield itself, these findings further support the research published by Dr. Fujio Agaki and team that even if you practice social distancing, a face shield alone is not sufficient to stop the spread of infection.

Dr. Fujio Agaki goes on to explain that when a person sneezes, a donut-shaped vortex ring is generated. This captures, “the microscopic droplets within the sneeze and transports them to the top and bottom edges of the face shield.”

The researchers concluded that face shields don't offer adequate protection against COVID-19 infection when worn alone, but the WHO (opens in new tab) advises that they can work when worn in combination with a protective face mask and used in tandem with social distancing and frequent hand washing.

Why face shields alone won’t protect you from COVID-19, new study says

(Image credit: Getty)

The best face masks to help slow the spread

To lower the risk of COVID-19 transmission, the CDC recommends (opens in new tab) that you wear a face mask any time you’re in public or are around people outside of your household. But with so many different types to choose from, how do you know which ones are the most effective?

For the general public who are healthy, not considered at risk, and who live in areas that don't have active transmission of the coronavirus, the CDC advice is to opt for a cloth face mask with a high thread count. Various studies (opens in new tab) also back this. So look for tightly woven 100% cotton face coverings and test the weave by holding it up to the light - if you can easily see the individual fibers, it’s not likely to be a good choice. 

Two to three layers of cloth with a high thread count have been shown to block between 50-80% (opens in new tab) of small droplets and particles. That type of covering, coupled with social distancing and frequent hand washing, is a good combination. Silk is also proving to be an effective and breathable option for those who do not like the feel of cloth coverings. 

Ditch the bandana
New research (opens in new tab) out of Duke University found that bandana masks, often used by runners, resulted in a higher number of respiratory droplets because the material breaks down large droplets into smaller particles that can then easily be inhaled. So the general advice now is to avoid bandana masks, also known as gaiter or fleece masks, as these do not offer adequate protection.

Instead, opt for a mask with two or more layers of washable and breathable fabric, as this will make breathing easier and more comfortable. Ensure it completely covers your nose and mouth and secures firmly under your chin. It also needs to fit snugly against the sides of your face without gaps, this will reduce the likelihood of you inhaling any infected droplets.

Where to buy protective face masks online

Reusable masks are suitable for most people under the age of 60 who are considered medically healthy. When buying one, look for coverings that have comfortable ear loops or behind the head ties, especially if you need to wear a mask for long periods. 

Those with a filter pocket are also more effective than those without. We love the new IF filter mask range at Vistaprint (opens in new tab), as there are plenty of designs to choose from and they come with either a permanent filter or a replaceable filter, depending on the type you buy. As the holidays approach, we're also seeing more festive face masks (opens in new tab) for kids and adults.

These retailers also have a range of disposable and reusable face coverings and masks in stock for home delivery:

For more health content, see our guides to the Best health insurance companies (opens in new tab) and the Best Medicare Part D plans (opens in new tab) to see how coverage could benefit you. For mask care, learn how often you should wash your face mask (opens in new tab)

Kathryn is a freelance health and wellness writer who is passionate about the mind-body connection, the role of food as medicine, and exploring how we can live in more sustainable and humane ways. A lover of the natural world, she’s at her happiest when walking the beach, staring out at the ocean, or when sat amongst lakes and mountains. For Top Ten Reviews, Kathryn covers more of our in-depth health content, ranging from diabetes news to vision care. And it isn’t just human wellness Kathryn is interested in - she also writes about the health of our furry friends over at our sister site PetsRadar.