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Glasses Against transmission of SARS-CoV-2 in the community (GLASSY): a pragmatic randomized trial

Background Observational studies have reported an association between use of eye protection and reduced risk of SARS-CoV-2 infection and other respiratory viruses, but as for most non-pharmaceutical interventions for infection control, no randomized trials have been conducted. We conducted a randomized trial to evaluate the effectiveness of recommending the use of glasses in public as protection against being infected with SARS-CoV-2 and other respiratory viruses. Methods and findings This was a pragmatic, randomized, trial in Norway from 2 February to 24 April 2022 where all adult members of the public who did not regularly wear glasses, had no symptoms of COVID-19 and no COVID-19 in the last 6 weeks, were eligible. Participants randomized to the intervention group were asked to wear glasses (e.g. sunglasses) for 2 weeks when close to others in public spaces. The primary outcome was positive COVID-19 test result notified to the Norwegian Surveillance System for Communicable Diseases (MSIS). Secondary outcomes included positive COVID-19 test result based on self-report and episode of respiratory infection based on self-report of symptoms. We randomized 3717 participants. All were identified and followed up in the registries and 87% responded to the end of study-questionnaire. The proportions with a notified positive COVID-19 test in the national registry were 3.7% in the intervention group (68/1852) and 3.5% (65/1865) in the control group (95% CI for risk difference -1.0% to 1.4%; relative risk 1.10, 95% CI 0.75 to 1.50). The proportions with a positive COVID-19 test based on self-report were 9.6% and 11.5% (95% CI for risk difference -3.9% to 0.1%; relative risk 0.83, 95% CI 0.69 to 1.00). The risk of respiratory infections based on self-reported symptoms was lower in the intervention group (31% vs. 34%; 95% CI for risk difference -3.3% to -0.3%; relative risk 0.90, 95% CI 0.82 to 0.99). Conclusions: Our results indicate that asking people to wear glasses may protect the public against respiratory infections, but the findings are not certain, and the study needs replication. Although the evidence is uncertain, and the effect probably modest at best, wearing glasses may be worth considering as one component in the infection control toolbox since it is a simple, low burden, and low-cost intervention, with few negative consequences.