CDC: TWO LAYERS… NOT THREE

On 10 October, the CDC published a study titled, “Effectiveness of Cloth Masks for Protection Against Severe Acute Respiratory Syndrome Coronavirus 2.”
The study concludes, “All masks tested showed some ability to block the microbial aerosol challenges although less than that of medical masks.” Another study found that homemade cloth masks may also reduce aerosol exposure although less so than medical masks and respirators. Masks made of cotton and towel provide better protection than masks made of gauze.
“Although cloth masks are often not designed to fit around the face, some materials may fit snugly against the face. One study found that the use of nylon stockings around the mask improved filtration.”
Contrary to the Association of American Physicians and Surgeons who say, “Cloth masks must be 3 layers, plus adding static electricity by rubbing with rubber glove,” on the CDC website, they say, “Masks with at least 2 layers of fabric are most likely to reduce the spread of COVID-19.”
TRENDPOST: While the above update by the CDC might sound like an endorsement of cloth masks, a closer reading shows otherwise. Note the phrases “some ability” and “may also reduce aerosol exposure.”
The words “some” and “may” are clearly not conclusive.
Nowhere in the study do the authors provide any data to counteract the conclusion from the 2015 Vietnam study, which showed that 97 percent of the influenza virus present at that time penetrated cloth masks. Furthermore, the CDC study ends with this “faint praise”: “The general public should be educated about mask use because cloth masks may give users a false sense of protection because of their limited protection against acquiring infection.”