Can indoor concerts ever be safe again?

Employees are headed back into the office, children are going to summer camp. The post-pandemic daily routine may soon look like 2019.

But what about the pure joy of singing along to a favorite artist, packed closely in a sea of thousands of fans? When will live music return?

A Tuesday night sunset concert at the Red Rocks Amphitheatre in Colorado was a welcome sight to many music lovers, including concertgoer Melinda Murphy, a teacher from Denver.

Murphy told CNN that if that same concert had been indoors, she might not have attended. The idea of being in a crowd inside “still creeps me out a little bit … indoors is a little too tight for me,” she said.

To attend a large, live music event inside, Murphy said she would need to know the venue capacity and social distancing plans before attending, and would wear a mask despite being fully vaccinated.

“I don’t believe everyone that’s going around in public now without a mask has been fully vaccinated,” she told CNN as the music played behind her.

The US Centers for Disease Control and Prevention’s revised guidance enabling fully vaccinated people to go maskless indoors and outdoors has spurred the desire and ability to return to normalcy, and to concerts.

“We’re seeing massive pent up demand for concerts globally,” Joe Berchtold, president of Live Nation, one of the world’s largest entertainment companies, told CNN’s Julia Chatterley Tuesday.

But the latest data from the Axios-Ipsos Coronavirus tracking index found that 37% of adults consider attending a concert indoors to be a large risk, 48% calling it a small to moderate risk, and 14% said it was no risk at all.

So how risky are indoor concerts, actually?

Large indoor events after COVID-19

Indoor sports leagues like the NBA have recently increased their attendance capacity, but concerts create a different set of circumstances. After a COVID-19 outbreak in an Australian church, researchers blamed it on poor ventilation, the infectiousness of the primary patient, and an enhanced ability of the virus to spread fueled by the act of singing.

“Singing has been demonstrated to generate more respiratory aerosol particles and droplets than talking,” the researchers wrote in a report published in the CDC’s Morbidity and Mortality Weekly Report.

There are few places that might be less pandemic-friendly than a live, indoor concert with thousands of fans singing along all at once. After months of social distancing, COVID-19 restrictions and lockdowns, some scientists decided the best way to understand how the coronavirus might spread in large, indoor crowds would be to study just that.

There’s a growing body of scientific literature that shows that with the right COVID-19 mitigation measures, large, indoor concerts could be held safely. But some scientists — including those leading the studies — have reservations on how broadly these findings may be applied.

A study of 1,000 people at an indoor live music event in Barcelona last December found that the concert led to no cases of COVID-19 transmission, according to a recent publication in the Lancet Infectious Diseases journal.

Attendees were required to take COVID-19 tests before entering, and were required to wear N95 masks the entire time, but could sing and dance with no social distancing during the live performances. The venue enhanced ventilation and implemented crowd directing and control, and participants needed to use two smartphone apps for contact tracing and communicating test results after the event.

However the study’s lead author, Dr Josep Llibre of the Germans Trias i Pujol University Hospital in Barcelona said the study’s results need to be taken into context.

“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. As a result, our study does not necessarily mean that all mass events are safe,” he said.

The trial took place December 12, 2020 — before both widespread transmission of COVID-19 variants and vaccinations.

Llibre says more research on large live indoor events is needed because findings, he believes, would be different depending on how prevalent the virus is in a community.

“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,” Llibre added.

Findings of the Barcelona study could serve as a model for events in countries with lower vaccination rates and existing mask requirements, but for highly vaccinated countries in the process of walking back COVID-19 requirements, the findings are most likely no longer applicable.

For a maskless, live concert model involving a partially vaccinated population, look no further than the United Kingdom. In April and May of 2021, the UK government sponsored a series of nine large, multi-day live events known as the Events Research Programme (ERP). They are meant to inform the UK government’s “roadmap” to COVID-19 recovery.

“The Roadmap describes plans to explore when and how events with large crowd sizes, less social distancing, or in settings where transmission risk is high without mitigation, may be able to return safely,” according to the UK government’s ERP website.

One ERP event in Liverpool was an indoor nightclub that saw between 3,000 and 4,000 local Liverpool attendees over two nights. Participants were required to take a COVID-19 test before entry, but did not have to wear masks or socially distance during the event. Attendees were asked to take a second COVID-19 test five days later. Researchers traced all positive cases, and monitored the nearby communities for any uptick in COVID-19 cases.

According to the University of Liverpool, nine cases of COVID-19 related to the nightclub trial were identified, though it’s not entirely clear those infections happened at the concert, and “the results showed there was no evidence of any substantial spread of the virus around the pilot events.”

Professor Iain Buchan, executive dean of the Institute of Population Health at the University of Liverpool and leader of the Liverpool nightclub event, told CNN that large indoor events should continue to require COVID-19 tests if the vaccination status of the crowd is unknown.

“Large events, especially if indoors and without social distancing or face coverings, should be treated as potential outbreaks and have all reasonable testing and other risk-mitigation measures in place … until such time that infection rates are low enough, and variant concerns are within reasonable limits. The Liverpool events were run at a time of low background risk. Testing is an important part of risk-mitigation,” Buchan told CNN in an email.

Erin Bromage, University of Massachusetts Dartmouth associate professor of biology, created the COVID-19 safety plan for the live Academy Awards, and has often consulted on how to safely conduct large events. He agrees testing is essential to the safety of large crowds congregating indoors while virus is still present in the community.

“If it was an indoor live event, I would be incorporating the rapid antigen tests, those cheap tests that cost $5. I would be incorporating them into the ticket price and having people doing those on the way in,” Bromage said during a phone interview from a movie set where he was a COVID-19 consultant.

But Bromage doesn’t believe protocols were properly tested in either the Barcelona or the UK studies because neither allowed anyone testing positive for COVID-19 to attend the events.

To really test that “what they did worked, it’s to find out that there was one or two infected people inside that space, and then there was no transmission. Because otherwise, you have no clue if the protocols worked,” he told CNN.

Bromage believes creating a quality indoor air environment by improving ventilation and lowering transmission risk should be the top priority for every indoor venue hoping to host any large, live events.

Bromage and UK and Barcelona event study leaders all agree that the safety of large, indoor concerts needs to be evaluated in the context of local community spread of COVID-19.

That’s what Live Nation told CNN it will be doing.

“We continue to follow guidance from local officials on requirements, which will naturally vary by region. We operate in over 40 countries, so it’s not one size fits all. But the good news is, as events return we will be welcoming everyone back to the concerts they know and love,” Live Nation told CNN in an email.

For those who still feel attending large music events are still a bit too risky, the pandemic has expanded access to live streamed concert experiences, so we can all get back to enjoying the music we love, in whichever way feels right to you.