The Protective Effect of Mask Wearing Against Respiratory Tract Infections

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.

Inclusion criteria

• Are at least 18 years of age
• Are willing to be randomized to wear, or not to wear, face masks outside their home when close to others for a 14-day period
• Provide informed consent

Exclusion criteria

• None