Twitter is shuttering its headquarters and halting all reopening plans just two weeks after it began allowing staff to return to the office, the company said Wednesday, as employers nationwide struggle to restore in-person work while coronavirus cases spike and vaccination rates plateau.

Twitter is closing its San Francisco headquarters and New York offices immediately, and will “pause future office reopenings,” a Twitter spokesperson told Forbes in a statement.

The company cited the Centers for Disease Control and Prevention’s new guidance Tuesday urging all Americans — regardless of their vaccination status — to wear masks indoors in communities with substantial levels of Covid-19 transmission, a list that currently includes San Francisco and all five New York City boroughs.

This closure comes just 16 days after Twitter reopened its New York and San Francisco offices following more than a year of mandatory work-from-home orders, though the company still allowed staff to work from home: “We aren’t asking everyone to return. Ever,” Twitter CFO Ned Segal tweeted in mid-July.