The linked study has garnered massive commentary on social media, mostly saying it proves that masks work. Most commenters read a news story, some may have read a press release, and a few read the study text.
As always, it is important to read the details. In this study (linked below), “cloth masks” were a layer of blown polypropylene and 2 layers of woven cloth. In the U.S. a “cloth facial covering” as defined by the CDC in April of 2020, was woven fabric such as masks made from pillow cases, t-shirts, bandanas and other fabric materials – not having a blown polypropylene layer.
Blown polypropylene, unlike woven fabric, has a random pattern of fibers and has different filtering characteristics than woven fabrics.
The “blown polypropylene + woven fabric” mask reduced Covid disease (in the study population) by 5%. The study did not test woven fabric-only cloth masks, which ostensibly, would be expected to perform worse than those with the blown polypropylene layer.
And the confidence interval goes from below zero to just above – that is, its possible their Rolls Royce “cloth” masks made the spread even worse.
Naturally, the media morons say this study proves that masks work. Can they even read?
The study seems to affirm what I’ve said since spring of 2020 – the available pre-pandemic studies found N95s have high effectiveness, surgical masks have less effectiveness, and cloth (actual woven fabric cloth) has essentially no effectiveness.
Consequently, I am not seeing a lot of new findings in this study – mostly re-affirming past studies in the context of Covid-19.
Another oddity – surgical masks only work for those age 50+ and did not work for those age 50-. Some are asking if (a) older people were more likely to distance from others due to increased risk of age, or (b) there is an unknown factor at work and they sliced the data by age solely to find a statistically significant result for someone. Due to age demographics, the pool of people over age 50 is smaller than the pool of those 50 and under.