CNN fired three employees for coming to the office unvaccinated.

The cable news channel has mandated that all employees working in its offices or in the field be fully vaccinated. In a memo to staff Thursday, President Jeff Zucker said the network has “a zero-tolerance policy on this” and fired the three after learning this past week that they were coming to the office unvaccinated.

“You need to be vaccinated to come to the office,” he said. “And you need to be vaccinated to work in the field, with other employees, regardless of whether you enter an office or not. Period.”

CNN had thus far relied on an “honor system” and hasn’t required employees to show proof they’ve been inoculated. In the weeks ahead, providing evidence of vaccination may become a formal process across CNN’s parent company, AT&T’s WarnerMedia, Zucker said.

The network is also delaying employees’ return to offices from Sept. 7 to “early to mid October” given the resurgence of the pandemic, Zucker said. Most of CNN’s U.S. locations are open on a voluntary basis for employees who are fully vaccinated.

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