No attendees at an indoor concert that employed rapid COVID-19 lateral-flow screening, N95 respirators, and a well-ventilated venue tested positive for COVID-19 in the next 8 days, showing no increased virus transmission risk associated with the event, according to preliminary findings from a randomized, controlled trial published yesterday in The Lancet Infectious Diseases.
A team led by researchers from the Germans Trias i Pujol University Hospital (GTPUH) in Barcelona, Spain, compared the coronavirus infection rate in 465 concert-goers aged 18 to 59 who were screened for COVID-19 and fever before entry and wore an N95 respirator throughout the event with 495 participants who were screened and then asked to go home. No concert-goers or 58 staff members tested positive 8 days after the event, compared with 2 in the control group.
"Our study provides early evidence that indoor music events can take place without raising the risk of SARS-CoV-2 transmission when comprehensive safety measures are in place, but it is important that our findings are considered in light of the situation in Spain at the time—when cases were not high and many restrictions were in place, senior study author Josep Llibre, MD, PhD, of GTPUH, said in a Lancet news release emailed to journalists.
"As a result, our study does not necessarily mean that all mass events are safe."
All venue entry, exit doors open
The concert took place in Barcelona on Dec 12, 2020, at a time when the prevalence of COVID-19 infections was low to intermediate, at 221 per 100,000 people, local travel was restricted, indoor gatherings were limited to six people, and COVID-19 vaccines had not yet been rolled out.
In a post-event questionnaire, concert-goers reported a satisfaction score of, on average, 8.6 out of 10 when asked to rate how well they were able to enjoy the performance. When asked how willing they would be to attend another event with the same mitigation protocols, the average score was more than 9 out of 10 (10 being most willing).
All participants were required to install two smartphone apps, one for contact tracing and one to receive their COVID-19 test results, complete health questionnaires before and 10 days after the event, and fill out a satisfaction survey.
Most concert-goers spent about 2 hours and 40 minutes inside the venue during the 5-hour event. In addition to two live music acts, there were two DJ performances. Drinks, including alcohol, were available in a separate room, and attendees could smoke outside in a limited-capacity area with physical distancing.
Concert attendees weren't asked to physical distance and were allowed to sing and dance in the concert hall, although the cloakroom was closed to prevent lines from forming. All entry and exit doors remained open throughout the event, and the venue was temperature controlled to make wearing an N95 respirator more comfortable.
Before the event, 28 people tested positive for COVID-19 on a transcription-mediated amplification test, 13 in the event group and 15 controls. Further lab tests confirmed that none were infected with live virus, indicating they were unlikely to spread COVID-19. All 28 had been diagnosed as having coronavirus about 7 weeks before the concert.
Future lines of research
Llibre cautioned that the strict protocols used in the study may be difficult to replicate or cost-prohibitive in other venues or in larger gatherings and that future research is needed to understand mass gatherings in other contexts of the pandemic.
"Widespread vaccination campaigns, changes in local incidence and the emergence of SARS-CoV-2 variants with higher transmissibility could all impact the interventions we tested, so we need more studies including larger numbers of people that explore different scenarios and policies that take into consideration the local context," he said.
First author Boris Revollo, MD, also of GTPUH, said in the release that while large gatherings are tied to a high risk of SARS-CoV-2 transmission, cancellation of these events has resulted in significant financial losses. "As societies look toward the possibility of safely resuming cultural activities, lateral flow tests, which can deliver results within 30 minutes and be taken on site, have been proposed as a means of screening people on entry to enable large events to take place," he said.
In a commentary in the same journal, Rosanna Peeling, PhD, and David Heymann, MD, of the London School of Hygiene and Tropical Medicine, said that the study is an important reminder of the need for more studies as diagnostic test innovation continues.
Such research could answer questions, they said, such as, "Would triple-layered masks have been sufficient? How does rapid antigen testing at entry compare with molecular screening within 72 h of entry? Does screening create bottlenecks with an increased risk of transmission among those not yet tested? … And the question of concern for all is whether existing [rapid diagnostic tests] are able to detect COVID-19 variants of concern and the role of vaccination."
