@MichaelSFuhrer @antizeroalt @Backtotravel22 I'm not aware of any covid studies finding zero, but maybe they're out there. Denmark found a small, not statistically significant, but positive effect, but only on the wearer, ignoring source control/transmission. Implied community effect would be larger.
@MichaelSFuhrer@antizeroalt@Backtotravel22我不知道有任何新冠病毒研究发现零，但也许他们在那里。丹麦发现了一个小的，没有统计意义的，但积极的影响，但只对佩戴者，忽略了源控制/传输。隐含的社区效应会更大。