It is indeed very surprising to see the sharp drop in Covid-19 cases in Germany. If I understand correctly, this is also not a randomized trial. I am not sure

It is indeed very surprising to see the sharp drop in Covid-19 cases in Germany. If I understand correctly, this is also not a randomized trial. I am not sure how they constructed the "control" group here to which they are comparing. It is a synthetic group where they extrapolate cases from n-7 days where n is the day of introduction of mandatory use of masks? It is hard to not be tempted to think about several confounding variables that could have played a role in the drop that is seen, like people being more vigilant, following distance guidelines, working from home more often, the list goes on. Nevertheless, it was an interesting read.