Live Nation, the world’s largest live entertainment company, has issued a “best practices” letter to artists empowering them to require proof of vaccination or a negative COVID test from fans attending their concerts.

“We are working to ensure we are reopening in the best way possible for staff, artists, crew, fans, and communities at large,” the letter (made public by Variety) explains. “Our teams have worked together to put new processes in place so that artists doing shows with Live Nation in the U.S. can require all attendees and staff to be fully vaccinated or show a negative test result for entry, where permitted by law.”

Live Nation’s letter referred to the vaccination requirement as a “great model,” noting that the protocol was used recently at their Lollapalooza festival.

“We know people are eager to return to live events and we hope these measures encourage even more people to get vaccinated,” the letter continued. “That is the number one thing anyone can do to take care of those around them and we are encouraging as many shows as possible to adopt this model.”

Though the company is “encouraging” artists to require proof of vaccination or a negative test, it is not mandating the new rules. Ultimately, the decision will lie in the hands of the performers and their respective teams.

In addition, Live Nation revealed that they will be requiring all of their own U.S. employees to “be vaccinated to enter one of our events, venues or offices – with limited exceptions as may be required by law.” The company rule will go into effect Oct. 4, when Live Nation’s offices are set to reopen.

The new “best practices” model comes as the safety of concerts and live events has once again come under scrutiny. The COVID-19 pandemic has seen a spike in cases recently, due largely to the highly-contagious Delta variant. Several prominent acts have canceled shows or pulled out of tours completely due to factors related to the coronavirus.

In July, outbreaks in Michigan and Oregon were directly tied to major outdoor festivals held in those respective locations.

“These events are the warning shot across the bow,” Dr. Emily Landon, the executive medical director for infection prevention and control at the University of Chicago Medical Center, explained to Rolling Stone. “Even though people are vaccinated, it looks like we may need to be more careful with super-crowded events.”

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