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UVM physician questions effectiveness of cloth masks to prevent virus’s spread

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    Alayna Sheets, middle, and her mother Suzanne Sheets organize their groceries on Tuesday, April 7, 2020, as an unidentified shopper walks into the Coop Food Store in White River Junction, Vt. Wearing masks for a few days, the Sheets ride the bus back and forth to the store. They have hardly been leaving home. "Every time you do go somewhere," said Suzanne Sheets, "it's a big thing that you don't bring any germs home with you." (Valley News - Jennifer Hauck) Copyright Valley News. May not be reprinted or used online without permission. Send requests to Jennifer Hauck

Valley News Staff Writer
Published: 4/11/2020 9:38:01 PM
Modified: 4/11/2020 9:37:58 PM

WEST LEBANON — State and federal health officials now recommend that most people wear cloth masks while in public, but their efficacy in preventing transmission of COVID-19 remains in question.

Dr. Tim Lahey, an infectious disease physician at the University of Vermont Medical Center, is abiding by the guidance, which officials announced earlier this month, but he questions the science behind it.

“There is no clear study showing that transmission is reduced, and some studies have even hinted the possibility of harm,” Lahey, who previously worked at Dartmouth-Hitchcock, said in an email.

Lahey took to Twitter to express his concerns last weekend after the Centers for Disease Control and Prevention and the Vermont Department of Health issued recommendations for members of the public to begin wearing cloth face coverings. Health officials said such masks will help to prevent asymptomatic people from spreading the virus that causes COVID-19, which was first identified late last year in Wuhan, China.

“CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission,” according to the CDC’s website.

Both state and federal officials emphasize that cloth masks are intended to be used in combination with other safety measures.

“We continue to think staying home and practicing physical distancing and good hand hygiene are the most important ways to stop the spread of COVID-19,” says guidance from the Vermont Department of Health. “By recommending that Vermonters use a face covering, we are adding one more action to help reduce the spread.”

Health officials do not recommend that members of the public wear surgical masks or N95 respirators as they say those supplies should be for health care workers. They also do not recommend masks for children under 2, or for others who have trouble breathing or cannot remove masks on their own.

In contrast with U.S. health officials, the World Health Organization does not recommend widespread mask wearing.

“There is currently no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can prevent them from infection with respiratory viruses, including COVID-19,” the WHO said in interim guidance issued on April 6.

The WHO warns that widespread use of masks in community settings may lead to a “false sense of security” that could cause people to ignore other measures such as hand washing and physical distancing. Other risks of widespread mask wearing may include self-contamination by touching and reusing masks; breathing difficulties caused by the mask; and the diversion of mask supplies needed for health care workers, according to the WHO.

As evidence that masks may cause harm, Lahey pointed to a 2015 study published in the British Medical Journal, which compared the effectiveness of surgical masks and cloth masks in preventing the spread of respiratory disease in a hospital setting in Vietnam. Cloth masks compared poorly with surgical masks and they recommended against the use of cloth masks in health care settings. The authors said the cloth masks retained moisture and had poor filtration.

But a 2008 study in the journal PLOS One found that cloth masks worn by volunteers in an experimental setting in the Netherlands prevented some droplets from being dispersed, the authors wrote. They also said that in a pandemic situation, people are likely to need to wear masks for weeks in order to see a difference in transmission rates.

For now, Lahey said that because of the lack of definitive information about whether or not masks are the right measure, “I’m going to sit here in a place of ambivalence and await the day when we know more.”

He wears a mask in public, he said, “because it seems like the popular thing to do.” And he said he tweets about the lack of data to support the measure “because I hope one thing we get out of this whole COVID-19 experience is a good education for the general public (and maybe even some of our politicians) on how to analyze weak evidence with a critical eye.”

Nora Doyle-Burr can be reached at or 603-727-3213.

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