Facemasks slow spread of coronavirus by 40 per cent, study shows

The research was able to use the staggered introduction of masks in shops and public transport across Germany as a natural experiment to test how effective they were. By looking at new cases in the days that followed, the researchers concluded that there is “strong and convincing statistical support” that the masks “strongly reduced the number of incidences”. However, other scientists cautioned that the findings were still not robust enough to support the widespread use of masks, arguing that too many other factors could explain the results. The study, published as a discussion paper for the Institute of Labour Economics, addresses one of the most controversial areas of science during the pandemic — one that has led to a split in opinion among researchers.