In this trial the researchers plan to recruit 25,000 volunteers to be randomly allocated either wearing sunglasses or ordinary glasses in public spaces where they are close to other people, or not wear glasses 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 results of COVID-19 tests during the trial period.

A systematic review of observational studies indicated that eye protection may be an effective measure to prevent SARS-CoV-2 infections. Randomized trials are needed to assess whether the observed associations are caused by protection of the eye or confounding factors such as other systematic differences between users and non-users of eye protection, co-interventions, or changes in COVID-19 incidence when comparisons were done over time.

This is a pragmatic, virtual, parallel group, 1:1 randomized, superiority trial. The researchers will recruit and randomize participants via an online portal. The trial will be fully remote and virtual without any personal interaction between investigators and participants. All members of the public are eligible who confirm that they are at least 18 years of age, do not regularly wear glasses, have not contracted COVID-19 since December 15th 2021, and are willing to be randomized to wear, or not wear glasses in public when close to other people, for a 2-week period. Persons who are dependent on visual aids but typically use contact lenses are eligible. The participants will be randomized (1:1) to wear glasses (sunglasses or other types of glasses) in public spaces when close to others (public transport, shopping centers etc.), or to the control group. The control group will be asked not to wear glasses in public spaces when close to others. The primary outcome is positive test for COVID-19.

The researchers aim to include about 25,000 participants to have a statistical power of 80% to detect a relative risk reduction of 25% for the primary outcome.

Inclusion Criteria:

• at least 18 years of age
• owns or can borrow glasses that can be used (e.g. sun-glasses)
• willing to be randomized to wear, or not wear glasses outside the home when close to others, for a 2-week period.
• provides informed consent

Exclusion Criteria:

• does regularly wear glasses (contact lenses are accepted)
• contracted COVID-19 after December 15th 2021.

From protocol:

The researchers intend to give full access to the full protocol, participant-level 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 2022, and an anonymous dataset for wide distribution at a later stage.

Data that are not fully anonymized will only be shared within the EU (due to data protection regulations).

No blinding was feasible, except for in the analysis phase. One member of our team (A.H.) provided the chief analyst (I.H.E.) with a data file in which group allocation was blinded. The chief analyst presented the main results to the project team members, who were also blinded to the group allocation (and data on use of glasses). We discussed how we would interpret the findings depending on whether one group or the other was the intervention group, and we prepared a short report that we posted online before unblinding ourselves to the group allocation.