As students return to school, are face shields effective against COVID-19?

In California, for example, the Orange County Health Care Agency, the Orange County Department of Education, and the Orange County school districts have developed a guide for returning to school. It says face covering is required from third grade through high school level, and is “strongly recommended” for children ages two through second grade. “A face shield is an acceptable alternative for children in this cohort who cannot use it properly,” the guide states.

Vanderbilt University in Nashville, Tennessee, among other universities, says it is comfortable to allow faculty members inside classrooms to wear a face shield without a mask. But research suggests that it may not be enough to prevent a teacher from spreading the coronavirus, especially if they are asymptomatic or presymptomatic. (Vanderbilt did not respond to request for comment.)

To reduce the risk of spreading COVID-19, the disease caused by SARS-CoV-2, it may be preferable to use high-quality cloth or surgical masks that are simple in design rather than face shields and masks equipped with valves. exhalation. according to an experiment published Wednesday by Physics of Fluids, a monthly peer-reviewed scientific journal that covers fluid dynamics.

The journal, which was first established by the American Institute of Physics in 1958, published the study, “Visualization of droplet dispersion for face shields and masks with exhalation valves,” to illustrate how the valve shield or mask affected droplet movement compared to wearing a mask without valves. Their conclusion: It may be preferable to use high-quality surgical or cloth masks with a simple, valveless design.

That’s in line with what the US Centers for Disease Control and Prevention has said: They recommend not wearing masks with valves or vents, because they can “allow virus particles to escape.” The CDC also recommends against wearing N95 respirators or surgical masks intended for healthcare workers.

“We focus on the smallest droplets as they can remain suspended for a long time and can contain enough virus particles to transmit COVID-19,” said Siddhartha Verma, one of the authors of the paper and assistant professor in the Department of Mechanics and Oceanic. Engineering at Florida Atlantic University in Boca Raton, Florida. “Even the best masks have some degree of leakage.” (Watch the video here).

In the experiment, face shields blocked the initial forward movement of a simulated cough or sneeze stream, but the expelled droplets moved around the visor with relative ease and spread over a large area, the experiment concluded. The experiment also suggested that droplets can pass through the exhalation valve of an unfiltered mask, “significantly reducing its effectiveness as a source control means.”

“As students return to schools and colleges, some have wondered if it is better to wear face shields, as they are more comfortable and easier to wear for longer periods of time,” said Verma. “But what if these shields aren’t that effective? Basically it would put everyone in a tight space with droplets that build up over time, which could lead to infections. “

Other universities I will not let students on campus without mask and to protect. The US Centers for Disease Control and Prevention does not recommend face shields as a substitute for masks: “It is not known what level of protection a face shield provides to people in the vicinity from the user’s respiratory droplet spray. There is currently insufficient evidence to support the efficacy of face shields. “

The CDC has reminded people to distinguish between masks and surgical masks. “Currently, those are critical supplies that must remain reserved for healthcare workers and other medical responders,” he says. “Masks are also not appropriate substitutes for them in workplaces where surgical masks or respirators are recommended or required and are available.”

While face shields and valve masks may be more comfortable than fabric masks, the CDC requires the use of a mask that covers both the nose and mouth, with the mask secured under the chin. It should fit your face comfortably. There should be no large openings or gaps around the nose, mouth, and sides of the face. Do not touch the mask while wearing it.

Some educational institutions are cautious in the use of face shields. Loma Linda University, a Seventh-day Adventist health sciences university in California, advises wearing face masks as the number one protection against COVID-19. “Prolonged exposure reduces the amount of shield protection,” according to this advice from the university’s health and wellness team.

The Vanderbilt University Public Health Advisory Task Force, in a statement on the university’s website, cited a “preliminary study” that provides sufficient evidence for the efficacy of face shields “as Vanderbilt intends. wearing them, combined with other protective measures (social distancing, lower classroom density, students with masks / covers, etc.). ”However, that preliminary study is actually a ‘point of view’ comment on protectors citing other research on face shields and the influenza virus, which is obviously different from coronaviruses.

That comment posted by the JAMA Network concludes: “It is unlikely that a random trial of face shields can be completed in time to verify efficacy. No 100% efficacy burden should be placed on face shields or any containment policy because this level of control is impossible to achieve and unnecessary to bring SARS-CoV-2 infection levels to a manageable range. “

Coronavirus update

As of Wednesday, COVID-19 had infected 25,836,032 people worldwide, which for the most part does not account for asymptomatic cases, and killed 858,436. The United States still has the highest number of COVID-19 cases in the world (6,088,187), followed by Brazil (3,950,931), India (3,769,523) and Russia (1,001,965), according to data aggregated by Johns Hopkins University.