SARS-CoV-2 transmission risk screening for safer social events: a non-randomised controlled study

There is an ongoing debate on the implementation of the COVID-19 passport throughout Europe. We sought to build and test a feasible prevention strategy to ensure low SARS-CoV transmission risk in public events. We conducted a non-randomised controlled study. The intervention group obtained a confidential digital certificate of very low capacity for transmitting SARS-CoV-2 and attended socio-cultural events in Girona (Spain) between 1 April and 21 May 2021. The primary care services and a network of pharmacies cooperated in providing the certification. A group of non-attendees was randomly selected from pseudonymised health records as controls. We estimated the incidences of SARS-CoV-2 infection and recorded the challenges in the process. Follow-up was complete for 1351 participants, who were matched with 4050 controls. Mean age of the study population was 31.1 years, and 53% of participants were women. Incidence rates of SARS-CoV infection at 14 days in the group of attendees and non-attendees were 15.9 and 17.7 per 100,000 person-days, respectively; the difference between incidences was - 1.8 (95% CI - 22.8, 19.3). Implementation problems were minor, and 89.2% of respondents to a survey were satisfied with the process. The incidence rate of SARS-CoV-2 infection was not different in the intervention and control groups. These results are in favour of establishing a COVID-19 certificate to attend public events, and connote feasibility of implementation at a population level.