Lollapalooza is the first big music festival to resume business as usual in the pandemic, and it did so this week despite spiking Delta variant cases all over the country. The first festival to be back on the calendar in the Bay Area is BottleRock Napa Valley, and unless things take a more serious turn, it's still happening in a month, from September 3 to 5.

Organizers of BottleRock announced Friday that, like at Lollapalooza, attendees will be required to show proof of vaccination to enter. As many bars around the Bay Area have also begun taking this step this week, the question now becomes whether masks should also be required — just as the CDC reveals new and compelling evidence that the Delta variant is spreading between vaccinated people in certain circumstances, like crowds. Also, the variant's infectiousness means that breakthrough infections among the vaccinated are much less rare than with previous variants.

Nearly 900 COVID cases have been confirmed, three quarters of them fully vaccinated, stemming from an outbreak in Provincetown over July Fourth, where vacationers gathered in both crowded indoor and outdoor spaces. And around 1,000 cases appear to have come out of an outdoor music festival in the Netherlands, though it's not clear how many of those attendees were fully immunized.

Those outbreaks and the CDC's new guidance this week about masks for the vaccinated make vaccine-at-the-door requirements feel already out of date, however experts continue to say that one's chance of getting infected after vaccination is much less than if you were unvaccinated, making vaccines still the best defense against the spread of COVID. According to CDC data, your chances of getting infected after being vaccinated and exposed stand at about one-eighth of the likelihood if you were not — however we don't know how high the likelihood rises when one is in a tightly packed space, indoors or outdoors.

Masks may be especially wise given the size of the crowds at BottleRock, which typically sees 120,000 attendees over three days (the Netherlands festival was only 20,000 people).

The lineup at BottleRock is slightly different than it was when the festival was originally set for May 2020, though many of the 80+ acts remain the same. Stevie Nicks and Miley Cyrus are both still on the bill, but Red Hot Chili Peppers, Dave Matthews Band, and Janelle Monae all had to cancel as the postponement reached over a year.

Foo Fighters, Megan Thee Stallion, and Guns N' Roses were all added to the lineup for this edition. As the Chronicle's Datebook notes today, Foo Fighters already canceled one July show in LA due to a confirmed COVID case among the band's touring crew.

Tickets for BottleRock are sold out, but there's an official exchange where people are offloading tickets they don't want.

Previously: BottleRock Rejiggers Lineup For Labor Day Weekend, Adds Guns N' Roses, Foo Fighters, Megan Thee Stallion

Top image courtesy of BottleRock (2019).