Three CNN staffers were fired for coming into the office while not being vaccinated against COVID-19, CNN head Jeff Zucker said in a memo to staff Thursday. “Let me be clear — we have a zero-tolerance policy for this,” he wrote, according to New York Times reporter Michael Grynbaum. “You need to be vaccinated to come to the office. And you need to be vaccinated to work in the field, with other employees, regardless of whether you enter an office or not. Period.”

The move appears to indicate a larger trend of requiring workers to be vaccinated before entering shared offices. The Washington Post said last week it would mandate vaccinations for all employees and visitors to its offices, while companies such as Disney and Walmart have announced mandates for their workforces. On Tuesday, New York City became the first U.S. city to require proof of vaccination to enter most indoor spaces.