Carl Heneghan and Tom Jefferson The Danmask study was a randomized controlled trial Do face masks work? Last week, Gov. Doug Burgum of North Dakota decided that masks could play a significant role in stopping COVID-19 and made masks mandatory in a number of public places. Iowa soon followed suit, bringing the total number of states with mask mandates to 36. But are these policies backed by the scientific evidence? Wednesday marked the publication of a long-delayed trial in Denmark which hopes to answer that very question. The ‘Danmask-19 trial’ was…