A Randomized Controlled Trial to Study the Transmission of SARS-CoV-2 and Other Respiratory Viruses During Indoor Clubbing Events (ANRS0066s ITOC Study)

Background In the context of the circulation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.617.2 (Delta) variant, vaccination re-authorized mass indoor gatherings. The Indoor Transmission of coronavirus disease 2019 (COVID-19) (ITOC) trial (ClinicalTrials.gov, NCT05311865) aimed to assess the risk of transmission of SARS-CoV-2 and other respiratory viruses during an indoor clubbing event among participants fully vaccinated against COVID-19.Methods ITOC, a randomized controlled trial in the Paris region (France), enrolled healthy volunteers aged 18-49 years, fully vaccinated against COVID-19, with no comorbidities or symptoms, randomized 1:1 to be interventional group attendees or control non-attendees. The intervention was a 7-hour indoor event in a nightclub at full capacity, with no masking, prior SARS-CoV-2 test result, or social distancing required. The primary outcome measure was the number of reverse transcriptase-polymerase chain reaction (RT-PCR)-determined SARS-CoV-2-positive subjects using self-collected saliva 7 days post-gathering in the per-protocol population. Secondary endpoints focused on 20 other respiratory viruses.Results Healthy participants (n = 1216) randomized 2:1 by blocks up to 10 815 attendees and 401 non-attendees, yielding 529 and 287 subjects, respectively, with day-7 saliva samples. One day-7 sample from each group was positive. Looking at all respiratory viruses together, the clubbing event was associated with an increased risk of infection of 1.59 (95% CI, 1.04-2.61).Conclusions In the context of low Delta variant of concern circulation, no evidence of SARS-CoV-2 transmission among asymptomatic and vaccinated participants was found, but the risk of other respiratory virus transmission was higher. Clinical Trials Registration. ClinicalTrials.gov, NCT05311865.Conclusions In the context of low Delta variant of concern circulation, no evidence of SARS-CoV-2 transmission among asymptomatic and vaccinated participants was found, but the risk of other respiratory virus transmission was higher. Clinical Trials Registration. ClinicalTrials.gov, NCT05311865. During an indoor clubbing with no restriction with participants fully vaccinated against COVID-19, and in the context of low Delta variant of concern circulation, we found no evidence of SARS-CoV-2 transmission but an increased risk of respiratory virus infection of 1.59.

Automated summary

In the context of low circulation of the Delta variant, there was no evidence of SARS-CoV-2 transmission among fully vaccinated participants in an indoor clubbing event. However, there was an increased risk of other respiratory virus infection.