Abstract
We congratulate the authors on successfully completing a randomised controlled trial of advice to mask in a community setting.1 This topic is notoriously difficult to study experimentally and few previous randomised controlled trials have been published. The main finding of this new study—that people advised to mask are significantly less likely to develop symptoms of a new respiratory infection over the next 17 days—is consistent with our recently published comprehensive review of existing evidence.2 The short follow-up period and lack of virologically confirmed outcomes and data on compliance are a limitation. While this study showed a significant advantage of surgical masks compared with no masks, it also demonstrated a failure rate of up to 70% (depending on the unknown non-compliance rate), which is not surprising given the airborne nature of respiratory viruses3 and the known propensity of surgical masks to leak.