Officials with a health department in central Illinois asked that anyone who attended Lollapalooza over this past weekend get tested for COVID-19 in the next few days.
The Champaign-Urbana Public Health District posted its recommendation on Facebook, writing, "If you were at LOLLAPALOOZA please go get tested for COVID on Wednesday, Thursday or Friday."
"This will help us shut down any local outbreaks before they get started," the post reads.
Chicago's largest musical festival - canceled last year due to the coronavirus pandemic - was allowed to return to Chicago's Grant Park from July 29 to Aug. 1 this year, at full capacity and with new health protocols.
But multiple infectious disease experts warned that Lollapalooza could lead to an increase in already rising metrics like COVID-19 cases and hospitalizations.
About 100,000 people attended the festival on each of the four days from Thursday to Sunday, organizers said Monday.
City officials billed it as the largest music festival happening in the world this year, with massive crowds and little to no social distancing or masking in the crowds at multiple performances.
To enter Lollapalooza, concert-goers were required to provide a printed copy of their COVID vaccine card, vaccine record or negative coronavirus test within 72 hours of entering.
"Over the course of the weekend, Lollapalooza entry gates saw an average of 91% proof of vaccination, 8% proof of negative COVID-19 tests and 1% denied entry for lack of proper documentation," organizers said in a statement Monday.
For those who are not vaccinated against COVID-19, a mask was required while inside the festival at all times. And in a tweet Friday evening, Lollapalooza announced masks will be required at any indoor spaces beginning Saturday following a recommendation from Chicago city officials the day before, in line with new federal health guidance, that all residents over the age of 2 wear masks in public indoor settings, regardless of vaccination status.
Some experts have expressed doubt whether mask requirements and social distancing would be followed and warned that the festival could cause case rates to rise even more.
“I think a lot of people are going to get COVID at Lollapalooza,” Dr. Emily Landon, executive medical director for infection prevention and control at the University of Chicago Medical Center said earlier this week. “The real problem is not so much that a bunch of young people who come into Chicago getting COVID at this event. The real problem is them taking it back to places that have very low vaccination rates."
“Lolla has let us down with respect to how vigorously they’re restricting people based on the things that they sort of initially told us (about how) ‘we’re going to be really strict’ and now it’s like they’ve lightened up quite considerably on checking vaccines and negative tests,” she added.
Chicago Mayor Lori Lightfoot dismissed the remarks from Landon - who has previously appeared alongside the mayor to deliver updates earlier in the pandemic - as coming from "critics standing on the sidelines."
Experts at Northwestern University said they are bracing for a jump in infections during the coming weeks.
"It’s a recipe for disaster,” Dr. Tina Tan, a pediatrician and professor at Northwestern University's Feinberg School of Medicine, said in a statement. "You have people coming in all over from U.S., and even though the organizers are taking some efforts to mitigate infections, I don’t know how they’re going to enforce mask wearing, social distancing, handwashing..."
Despite an uptick in cases fueled by the delta variant, the Chicago Department of Public Health and Lollapalooza's own health experts decided it was safe to proceed with the festival, Lightfoot previously said.
At a news conference last week, Dr. Allison Arwady, the commissioner of CDPH, said there will "almost certainly" be some cases associated with the four-day concert series.
"I certainly know we're being a lot more responsible than many other settings, that are just as large, that are gathering around the country," the doctor said Tuesday.
Northwestern's infectious disease experts say they anticipate a spike in infections will occur next week, but remain optimistic for a good outcome.
“If everyone attending Lollapalooza is vaccinated or has a negative test, that’ll keep the numbers lower,” Dr. Robert Murphy, executive director of Northwestern’s Institute for Global Health, said. “And I hope that happens. Maybe it’s even made a lot of younger people get vaccinated in order to come."