No subsequent COVID-19 infections detected after mass-screening at indoor event

15th June 2021

The mass-screening of individuals attending an indoor event without social distancing, could pave the way for the reactivation of cultural events.

Mass gatherings are potentially super-spreading events for viruses and have been cancelled in most countries to reduce transmission of COVID-19. A major problem during a mass gathering event is the difficulty identifying those who are infectious. Moreover, given that PCR testing is laboratory-based and therefore has a long turnaround time, mass testing of attendees to any such event becomes impossible. However, the use of point-of-care antigen-detecting rapid diagnostic testing (Ag-RDT) could provide a workable solution. Since this tool has not been tested under controlled conditions, a team from Barcelona, Spain, performed a randomised trial to test the effectiveness of a prevention strategy during a live indoor music event. The assumption of the study was that point-of-care mass-screening for infected individuals and regular preventative measures would reduce the risk of transmission of COVID-19. For the present study, adults (18 years and over) were recruited via social media and those willing to participate were tested with samples from nasopharyngeal swab, using the Ag-RDT approximately 12 hours before the music event. Those with a negative test were then randomised to either attendance or return to normal life (i.e., the control group). In addition, a transcription-mediated amplification (TMA) test was also performed and reported to participant’s smartphones, after 24 – 48 hours. During the event, participants had their temperature checked at entry to the venue and were given an N95 mask which had to be worn throughout the event but could be removed in the bar area for drinking. The primary outcome was the difference in incidence of PCR confirmed COVID-19 infections between the control and intervention (i.e., event attendees), 8 days after the event.

Findings
A total of 960 individuals who expressed an interest in attending the event tested negative and were included in the final analysis; 495 were allocated to the intervention and 465 the control group. For the group as a whole, the mean age was 33.6 years (82% male). Despite a negative Ag-RDT test at baseline, 28 individuals had a positive TMA result although subsequent PCR testing confirmed only 2 positive results (both in the control group). Interestingly, none of the music event attendees developed a positive PCR test on day 8 and only 2 in the control group, one of whom had been diagnosed with COVID-19, four days after randomisation.

In their discussion, the authors noted that even though participants at the event were allowed to sing and dance (albeit wearing a mask), even without social distancing, none developed COVID-19. Their study was the first to provide evidence on the safety of indoor events, provided that some mitigation strategies (i.e., mask wearing and mass-screening) were deployed. They concluded that their findings should pave the way for reactivation of cultural activities.

Citation
Revollo B et al. Same-day SARS-CoV-2 antigen test screening in an indoor mass-gathering live music event: a randomised controlled trial. Lancet 2021