Organizers of Chicago's Lollapalooza festival have a strict message for music lovers who want to attend all four days of the event: Get vaccinated, or get tested for COVID-19 more than once during the weekend.
The outdoor event, which typically draws hundreds of thousands of fans over the course of the festival, runs from July 29 through Aug. 1. To gain entrance to the festival, ticket holders must either show a printed copy of their vaccine card, a vaccine record or a negative COVID-19 test taken in the past 72 hours.
But because the festival runs for 96 hours, for the unvaccinated or partially vaccinated, one negative test won't cut it. Attendees will need to get tested again and bring new proof of a negative COVID-19 test if their initial one was taken more than 72 hours ago.
In addition to the testing or vaccination requirements, Lollapalooza recommends that attendees "avoid physical contact with people outside of your party" and limit consumption of alcohol and other substances.
"Consuming alcohol or substances may make you less likely to follow COVID-19 safety measures," the festival website notes.
"I do think there is going to be a significant risk of transmission at a tightly packed event such as Lolla, unfortunately," Dr. Zachary Rubin, a clinical immunologist, told ABC News' Chicago station WLS-TV.
Free masks will be available at the entry, at guest services and at the festival's medical tents. Anyone who is not vaccinated should wear a mask and maintain six feet of social distance from anyone not in their group during the event.
Chicago's vaccination rate is on par with the national average. As of Sunday, 58% of residents had received at least one dose, and 52% were fully vaccinated, according to city data. By comparison, 57% of Americans have gotten at least one shot, and 49% are fully vaccinated, according to the Centers for Disease Control and Prevention.
Beyond Chicago, the highly transmissible delta variant is surging nationwide, with nearly every state in the country reporting increasing COVID-19 infections, according to data from the Department of Health and Human Services.
The CDC now categorizes the U.S. as having "high" community transmission, with nearly 62% of U.S. counties currently reporting high or substantial transmission.
ABC News' Arielle Mitropoulos contributed to this report.
Lollapalooza COVID-19 rules depend on vaccination status originally appeared on abcnews.go.com