Starbucks will require U.S. workers to get vaccinated against COVID-19 or undergo weekly testing to comply with federal rules, the company told employees Monday.

More companies are expected to make similar announcements as the Jan. 10 deadline to comply with President Biden’s vaccine-or-test mandate approaches. Companies with 100 or more employees must collect their workers’ vaccination status by Jan. 10 and enforce the testing alternative by Feb. 9.

Starbucks told its 220,000 U.S. employees in a Monday memo that they must show proof of vaccination or pay for their own weekly testing, according to Reuters. Starbucks Chief Operating Officer John Culver previously told employees in a Dec. 27 letter that the company was preparing to enforce the Biden administration mandate.

“My responsibility, and that of every leader, is to do whatever we can to help keep you safe and to create the safest work environment possible,” Culver wrote. “The vaccine is the best option we have, by far, when it comes to staying safe and slowing the spread of COVID-19.”

The vaccine-or-test mandate, which would impact 80 million Americans, has survived an onslaught of challenges from Republican officials, conservative groups and some business interests.

The rule had been blocked by a court order until last month, when another federal appeals court allowed it to go into effect. The Supreme Court will hear challenges to the vaccine-or-test mandate and vaccine requirement for health care workers this week.

The Biden administration has argued in court that the rule will save thousands of lives by encouraging more Americans to get vaccinated. The court battle comes amid an unprecedented surge of new COVID-19 cases driven by the omicron variant.