Covid-19: New evidence on face masks

A few months back I wrote an article about the state of the evidence on face masks. At that point, there were no good studies looking at the effectiveness of face masks in preventing the spread of covid-19 specifically, but there was a systematic review that looked at all randomized trials that had been done on face masks for the prevention of respiratory infections more generally. That review found that surgical face masks reduced the probability of getting a respiratory infection by around 4% in absolute terms (17% in relative terms). read more