>There's some evidence that home made cloth masks are worse than nothing. >MacIntyre 2015 That paper is studying whether wearing a mask protects the user of t

>There's some evidence that home made cloth masks are worse than nothing. >MacIntyre 2015 That paper is studying whether wearing a mask protects the user of the mask. But the purpose of universal wearing of cloth masks is mainly to protect people ­from­ the wearer. (Many people infected with COVID-19 are contagious without showing symptoms.) And the study wasn't really "cloth mask vs no mask". It was "cloth mask" vs "sometimes wearing a medical-grade mask and sometimes wearing no mask": > (1) medical masks at all times on their work shift; (2) > cloth masks at all times on shift or (3) control arm > (standard practice, which may or may not include mask > use). Standard practice was used as control because the > IRB deemed it unethical to ask participants to not wear > a mask. ... > Cloth masks resulted in significantly higher rates of infection than > medical masks, and also performed worse than the control > arm. The controls were HCWs who observed standard practice, > which involved mask use in the majority, albeit with > lower compliance than in the intervention arms. The > control HCWs also used medical masks more often than cloth masks.