CDC: Double Masking Improves COVID-19 Prevention Efforts

Putting on a cloth mask over a surgical or medical mask can help reduce the spread of the coronavirus, the Centers for Disease Control and Prevention says. 

The agency updated mask guidelines Feb. 10 based on studies it did to determine how to improve mask efficacy. The agency looked at wearing a cloth mask over a medical procedure mask (often called a surgical mask, but not an N95) and whether knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face would reduce risk.

Both modifications improved the effectiveness of masks. According to the CDC’s experiments, an unknotted medical procedure mask blocked 42 percent of the particles from a simulated cough. A cloth mask blocked 44.3 percent. Knotting the surgical mask alone blocked 63 percent of particles. When the cloth mask was combined with the knotted surgical mask, it blocked 92.5 percent of particles.

Early in the pandemic, public health officials were reluctant to recommend masks. While some people are skeptical of the effectiveness of masks, a there’s clear evidence that masks reduce the transmission of the coronavirus. In fact, the Proceedings of the National Academy of Sciences of the U.S., which recently published a review of studies about masks and COVID-19 transmission, concluded:

“The preponderance of evidence indicates that mask wearing reduces transmissibility per contact by reducing transmission of infected respiratory particles in both laboratory and clinical contexts.”

Some study highlights:

• In states where there were mask mandates, hospitalizations declined after the mandate. 
• In counties with mask mandates, COVID infections declined; in counties without them, incidences increased.
• Masks were 79 percent effective at preventing household transmission, if used by all members of the household before symptoms showed.

Studies also show that masks not only protect people around the wearer, but the wearer themselves.

The new CDC studies, which you can find here, do not recommend double masking with an N95 or KN95 mask. It also doesn’t recommend doubling up surgical masks.