The trial was designed to detect at least a 50% protection against a SARS-CoV-2 infection given by mask wearing, assuming that the incidence rate in people not wearing masks was 2% per month. That assumption turned out to be correct, as the authors found a 2% per month rate during the study, and therefore the sample size calculation carried out before the study was right. Since the research did not find a statistically significant result for the effect of masks on SARS-CoV-2 infection, the conclusion we must draw is that masks give a protection that is less than 50%. That is a very important message to give to the many people thinking that masks give a protection that is close to 100%. Should those people attend crowded enclosed spaces assuming that masks protect them, they would put themselves at risk.