“My mask protects you and your mask protects me.”
That statement has been part of messages from health officials about how masks can make an impact on the reducing the spread of COVID-19 as well as part of safety messages in retail establishments.
A scientific brief from the Centers for Disease Control (CDC) released Tuesday indicates that there may be some limited protection for the individual wearing the mask.
That brief was noted by Dr. Clay Runnels, chief physician executive at Ballad Health during the system’s weekly coronavirus briefing on Wednesday.
People are asked to wear masks to reduce the transmission of their respiratory droplets to others as a means of infection control, Runnels said. “If we have more people wearing masks, it will help control the transmission of the virus,” he added.
“This new study shows that it can also protect your in some degree as well, as it helps reduce the inhalation of droplets,” Runnels said.
Wearing cloth masks along with social distancing, frequent hand washing and avoiding large gatherings can help keep individuals from contracting the virus, he said.
This CDC scientific brief looks at both the effectiveness of cloth masks at blocking exhaled respiratory droplets that can carry the virus, and also its filtration properties to protect the wearer.
According to the brief on the CDC website, multilayer masks not only block the exhalation of most large droplets, they can also block fine droplets and particles, which increase in number with the volume of speech and specific types of sounds.
“Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles and limit the forward spread of those that are not captured,” the brief stated. “Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control.”
Studies also demonstrate the masks can also reduce wearers’ exposure through filtration, the brief stated. Although the effectiveness of various masks has varied widely across studies due to experimental design and particle sizes analyzed, multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloths, in some cases filtering nearly 50% of the fine particles.
The brief noted that the “real-world” effectiveness of masks are limited to observational and epidemiological studies.
One of the studies referenced in the brief includes an investigation of a high-exposure event, in which two symptomatically ill hair stylists interacted for an average of 15 minutes with each of 139 clients during an 8-day period. The study found that none of the 67 clients who subsequently consented to an interview and testing developed infection. The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.
Another study analyzed an outbreak aboard the USS Theodore Roosevelt, an environment notable for congregate living quarters and close working environments. That study found that use of face coverings on-board was associated with a 70% reduced risk of contracting the virus.
The brief also said investigations involving infected passengers aboard flights longer than 10 hours strongly suggest that masking prevented in-flight transmissions, as demonstrated by the absence of infection developing in other passengers and crew in the 14 days following exposure.
Seven studies are referenced in the brief that analyzed the benefit of universal masking in a community. Each analysis demonstrated that, following directives from organizational and political leadership for universal masking, new infections fell significantly and two of the studies also demonstration reductions in mortality.
Greene County Mayor Kevin Morrison issued an executive order last month that extends a mask mandate locally until Dec. 29.
The brief noted that an economic analysis by Goldman Sachs using U.S. data found that, given these effects, increasing universal masking by 15% could prevent the need for lockdowns and reduce associated losses of up to $1 trillion, or about 5% of gross domestic product.
The CDC brief noted that further research is needed to expand the evidence base for the effectiveness of cloth masks and to identify combinations or materials or layers that may provide greater blocking and filtering of particles as well as for comfort and durability. It also recommended that adopting universal masking policies can avert future lockdowns, particularly if combined with social distancing, hand hygiene and proper ventilation.