This study is a pragmatic, two-armed cluster randomized superiority trial including participants in Norway. Participants will be randomized to one of the following two arms: control group or medical masks in a 1:1 ratio. The primary outcome is self-reported respiratory infection.~The intervention is to ask participants in the intervention groups to wear face masks when close to others outside their home, e.g., in public spaces like shopping centres, and streets and on public transport. The control group will be asked not to wear face masks when close to others outside their home, e.g., in public spaces like shopping centres, and streets and on public transport. Participants will continue to use, or not use, face masks at work independent of which group they are allocated to.~The trial will be fully remote and without any personal interaction between investigators and participants.~The researchers aim to include about 4,000 participants to have a statistical power of 80% to detect a relative risk reduction of 30% for the primary outcome.
In this trial the researchers plan to recruit 4,000 volunteers to be randomly allocated either wearing face masks in public spaces where they are close to other people, or not wear face masks in such circumstances. For each participant the trial period is 2 weeks, after which they will be asked to complete a brief questionnaire which includes questions about whether they experienced the common cold, influenzas or COVID-19 symptoms during the trail period.