Meta has delayed its US office reopening date and mandated Covid-19 booster vaccines for employees returning to office.

For employees who opt to work from the office, the reopening date has been delayed. The new returning to office date is March 28, the tech giant said on Monday.

Meta currently requires all its U.S. employees coming to office to be vaccinated against the coronavirus. The company says it will watch if all workers returning to office have proof of their booster jabs.

March 14 is the deadline for employees to decide whether to return to the office, request to work remotely full time or request to work from home temporarily.

Workers who are not vaccinated for medical or religious reasons can request such remote work, a spokesperson said. He added:

“Employees who take no action can face disciplinary measures, including termination. Obviously, this would be a last resort.”

In December, the parent company of Facebook, Instagram and WhatsApp had offered an option to defer returning to office. This way Meta is joining the growing list of companies revamping reopening plans as Omicron surges.