Double masks may offer extra protection against coronavirus infection, CDC study says
Wearing two masks — a cloth mask over a surgical mask — as well as modifying a surgical mask by knotting its ear loops reduced a healthy person’s risk of catching coronavirus by more than 95%, according to a new Centers for Disease Control and Prevention study.
This is the first laboratory study from the CDC that tested the effectiveness of double masking and other creative alterations amid discussions to update public health messaging on appropriate face coverings as at least three more contagious coronavirus strains spread in the U.S.
Although the study’s findings suggest that double or tightly secured masks significantly reduce coronavirus exposure risk, the CDC says its study may not represent infection control in real-world settings outside the lab. The agency also warns face mask modifications may not apply to children, whose faces are smaller, or men with facial hair.
CDC Director Dr. Rochelle Walensky said Wednesday during a White House COVID-19 briefing that the new scientific evidence does not change CDC guidance on who should wear masks, however she said the agency has updated what kind of masks and mask accessories are appropriate on their website, including double masks, mask fitters and nose wires.
“The data in this report underscore the finding that good fit can increase overall mask efficiency. Multiple simple ways to improve fit have been demonstrated to be effective. Continued innovative efforts to improve the fit of cloth and medical procedure masks to enhance their performance merit attention,” the CDC said in its report released Wednesday.
“Until vaccine-induced population immunity is achieved, universal masking is a highly effective means to slow the spread of SARS-CoV-2 when combined with other protective measures, such as physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene,” the agency added.
White House coronavirus adviser Dr. Anthony Fauci has previously mentioned that layering two masks “just makes common sense” in terms of adding more protection against infection. But during a COVID-19 briefing last week, Fauci said the CDC was waiting for scientific evidence before making a recommendation.
The researchers used plastic heads placed in a 10-foot-by-10-foot room to simulate how people cough in real life, using a harmless salty liquid in particle sizes similar to those of the coronavirus to represent respiratory droplets.
The first experiment found that one surgical mask worn normally blocked 42% of particles from a simulated cough and one cloth mask alone blocked about 44% of particles, while a cloth mask covering a surgical mask (double masking) blocked about 93% of cough particles.
A second experiment included two mannequin heads, one representing a coronavirus-infected person and the other a healthy individual.
When the sick person wore a cloth mask over their surgical mask, or knotted the ear loops of just one surgical mask and tucked in any extra material to eliminate open gaps, the unmasked healthy person’s exposure reduced by about 82% and about 63%, respectively.
When the sick person did not wear any mask and the healthy individual wore either the double mask or modified surgical mask, the healthy person’s exposure risk dropped by 83% and about 65%, respectively. This suggests that wearing a face covering, even if other potentially sick people around you are not, still offers some protection against infection.
And in the best possible scenario, where both the sick and healthy person are fitted with either double masks or modified surgical masks, exposure risk to the healthy individual was lowered by about 96% for both mask options, according to the study.
“Although use of double masking or knotting and tucking are two of many options that can optimize fit and enhance mask performance for source control and for wearer protection, double masking might impede breathing or obstruct peripheral vision for some wearers, and knotting and tucking can change the shape of the mask such that it no longer covers fully both the nose and the mouth of persons with larger faces,” the CDC said.
This story was originally published February 10, 2021 at 8:00 AM with the headline "Double masks may offer extra protection against coronavirus infection, CDC study says."
