Surgical face masks to prevent respiratory symptoms

Early in the covid-19 pandemic, face masks were promoted as an important non-pharmaceutical intervention.1 Masking makes intuitive sense. Most cultures teach children to “catch your cough” and “cover your mouth when you sneeze.” In many Asian countries it was a prepandemic cultural norm for people to wear masks. However, many commentators have reasonably asked, “do masks work, and should they be recommended?” These seemingly simple questions have proved challenging to answer, and, in some places, policies on masking—especially mask mandates—are controversial and politicized.2 The weight of randomized and observational evidence to date suggests that masks probably reduce the risk of covid-19 infection.3

Now, in the linked paper, Solberg and colleagues (doi:10.1136/bmj-2023-078918) report an impressive randomized controlled trial conducted in Norway in early 2023.4 The participants—4647 adults, with an average age of 51 years—were assigned to either wearing or not wearing a surgical face mask when they were likely to encounter others in public spaces. After only 14 days those randomized to wear surgical face masks had an absolute 3% reduction in the incidence of symptoms consistent with a respiratory tract infection (8.9%), compared with controls (12.2%; 95% confidence interval for the difference, −5.2% to −1.3%). The internal …