The Protective Effect of Mask Wearing Against Respiratory Tract Infections

The Protective Effect of Mask Wearing Against Respiratory Tract Infections: a Pragmatic Randomized Trial

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.

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.

Sequence generation. We will use a simple 1:1 randomization by means of computer-generated random numbers. The allocation will be concealed as the participant themselves will be directly informed of their allocation as soon as they have agreed to take part in the trial and have completed the online consent and baseline form. Generation of allocation sequence, enrolment of participants and assignment of participants will all be handled by the digital recruitment platform.

Participants in the experimental arm are asked 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 in the no intervention arm arm are 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.

We will compare the incidence of notified cases of COVID-19 (i.e. registered positive SARS-CoV-tests)

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

The researchers intend to give full access to the protocol, participant level-data dataset and statistical code to anyone who is interested, after securing that the dataset is fully anonymized.

The investigators expect to be able to share unidentifiable dataset with partners inside the European Union (EU) by May 2023, and an anonymous dataset for wide distribution at a later stage.