“The way to think about it is that it’s cumulative risk reduction,” he said, adding, “We cannot get the risk to zero, unfortunately, but we can reduce it markedly by vaccines, masks and, if people don’t want to wear masks, having them do a rapid test before getting together.”

Another safety precaution party-throwers are adopting: paring down the guest list, a painful measure for many.

In November, José Xicohténcatl, a public relations professional in Huntington Beach, Calif., who goes by Pepe, started planning a big company bash with a guest list of 100, the sort that the company used to have prepandemic. But then Covid cases started climbing in California.

The company decided to move the party to an outdoor space with heaters and to restrict attendance to employees only — no clients and no plus-ones. Mr. Xicohténcatl has asked guests to show proof of vaccination and booster or a negative test done in the past 48 hours.

His priority is to ensure that employees feel comfortable and safe, Mr. Xicohténcatl said.

“One of the things that we needed to do this year was make sure that we at least got some face time,” he said, adding that when cases started rising again it felt “like the Grinch stole Christmas.”

“We can’t get out and party anymore like we did in 2019,” Mr. Xicohténcatl said.

Newsday, the Long Island newspaper, pulled the plug on a newsroom party when Covid cases started rising in the area. The party, planned for mid-December, was to include an ugly holiday sweater raffle, a build-a-snowperson contest, a photo booth and an appearance by the newspaper’s mascot, Scoop.

Kim Grabina-Como, a spokeswoman for Newsday, said that the party was called off because “the health and safety of our employees have always been our No. 1 priority.”