'A cluster randomised trial of cloth masks compared with medical masks in healthcare workers' reported in April 2015 that rates of infection outcomes were highest with cloth masks including virus transmission and penetration; and concludes that cloth masks should not be recommended for healthcare workers, particularly in high-risk situations.
This study is revisited under the present COVID-19 situation.
Published in BMJ Open with doi: 10.1136/bmjopen-2014-006577