In a lab experiment, two artificial heads were placed six feet from each other and studied on how many coronavirus-sized particles were expelled and inhalled while wearing a variety of face coverings.
Researchers found that wearing one mask, either cloth or surgical, prevented 40 per cent of incoming droplets from being breathed in. When adding a surgical mask underneath a cloth mask, 80 per cent of incoming droplets were stopped.
The study then looked at what happened if both of the artificial heads double-masked while expelling and inhalling coronavirus particles. It found that about 95 per cent of particles were blocked.
Dr Rochelle Walensky, the CDC director, detailed these findings on Wednesday when speaking during the White House coronavirus breathing.
"The science is clear," she said. "Everyone needs to be wearing a mask when they are in public or when they are in their own home but with people who do not live in their household."
"This is especially true with our ongoing concern of new variants spreading in the United States," she said.
But the CDC director did not go as far as to recommend for all Americans to double-mask when out in public. Instead she said that the science proved a "well-fitting mask provide the best performance" when preventing the spread of the novel virus.
“With cases hospitalizations and deaths still very high, now is not the time to roll back mask requirements,” Dr Walensky said, adding, “The bottom line is this: masks work and they work when they have a good fit and are worn correctly."
The federal health agency suggested several options for Americans to improve how they wore masks when out in public. One option involved layering a surgical mask underneath a cloth mask. Alternatives were using masks with a nose wire or adding a mask fitter to assist in sealing the face shield over the nose and mouth.
"If the mask has a good fit, you will feel warm air come through the front of the mask and may be able to see the mask material move in and out with each breath," the CDC states in updated guidance released on Wednesday for how to "improve how your mask protects you."
Dr John Brooks, lead author of the new CDC study, cautioned that the data collected was in a laboratory setting, and it was not yet clear how these masking guidelines could alter when implemented in real life.
“But it’s very clear evidence that the more of us who wear masks and the better the mask fits, the more each of us benefit individually," he added.
Mask-wearing became prevalent within the first two months of the pandemic in the United States, but it's been met with some resistance from government officials and residents.
President Joe Biden implemented a national mask mandate on his first day in the Oval Office that applied to federal property and interstate travel, such as airports. But it was on state governors to implement mask mandates for their jurisdictions.
As of 1 February, 14 states and the District of Columbia have universal mask mandates. In Iowa, though, officials have decided to lift their mask mandate against guidance from health officials.
Jen Psaki, the White House press secretary, said on Wednesday during a press briefing that the Biden administration was not considering a double-masking recommendation despite the recent study.
“It doesn't actually issue definitive guidance on one mask versus two mask,” Ms Psaki said about the study. “Obviously if that's something they were to issue as official guidance, we listened to our health and medical experts.”
She added that study shows “that if a person has a loose fitting mask that they should consider options to improve that fit.”
The Biden administraiton was considering "a range of options" to "ensure that people who need masks the most, people who need this type of protection the most, receive it, but no decision has been no final decision has been made," Ms Psaki said.
This comes as the United States has prioritised a mass vaccination campaign to get all Americans vaccinated as quickly as possible amid new coronavirus variants spreading through the country. Health officials have implored people to continue to follow mitigation measures, such as mask wearing and social distancing, in the meantime.
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