Omicron leads ‘S.N.L.’ to do without an audience and a pop star to cancel her performance.

“Saturday Night Live” announced, just hours before showtime, that there would be no live audience on Saturday night “out of an abundance of caution” amid the surge of coronavirus cases in New York tied to the Omicron variant.

The show also wrote on Twitter that there would be “limited cast and crew,” but it did not say whether any of the cast members had tested positive for the virus.

“The show continues to follow all government safety guidelines in addition to a rigorous testing protocol,” it said, adding that those who had tickets to the taping at Rockefeller Center “would be getting more information soon.”

A person familiar with plans for the show said that some cast and crew either had tested positive or had been in close contact with people who had.

Saturday’s show, the last of 2021, was hosted by the actor Paul Rudd — his fifth time, which was the focus of the subdued opening. Tom Hanks, the Academy Award-winning star of “Forrest Gump,” took the stage and explained that though they had planned a special Christmas show, “Covid came early this year, so in the interest of safety, we do not have an audience and we sent home our cast and most of our crew.”

Tina Fey, a former cast member, and Kenan Thompson, a current cast member, then joined him to induct Mr. Rudd into the so-called Five-Timers Club for hosts. They closed the opening by explaining that the impromptu show would consist of new sketches taped earlier in the week and personal favorites from previous episodes.

Mr. Rudd joked, “It’s going to be a little bit like that new Beatles documentary — a lot of old footage but enough new stuff that you’re like, ‘OK, yeah, I’ll watch that.’ ”

The show was supposed to have included a musical performance by the English pop artist Charli XCX. She ended up canceling, explaining that she could not perform with so few crew members. “I am devastated and heartbroken,” she said in a statement of her own, adding: “It can’t happen this time but I’ll be back! I am currently safe and healthy but of course very sad.”

“Please look after yourselves out there and make sure you get vaccinated if you haven’t already,” she continued.

NBC declined to comment beyond the show’s statement.

“S.N.L.” normally tapes a dress rehearsal at 8 p.m. Eastern time on Saturday, and then the live performance airs at 11:30 p.m.

Mr. Rudd closed the show by thanking the cast and crew for working so hard under stressful circumstances.

“I know it wasn’t the Christmas show you expected, but that’s the beauty of this place. Like life, it’s unpredictable,” he said, as he and four others onstage wore face masks.

He finished by cracking a joke at Mr. Hanks’s expense. “As my good friend Tom Hanks once said in a movie, life’s like a big, weird chocolate bar: sometimes it’s delicious; other sometimes it’s got that orange cream filling in it,” he said. “And it’s like, OK, it’s not what I would have chosen, but it’s better than nothing.”