Just two weeks after reopening its New York and San Francisco offices, social media giant Twitter said Wednesday that it will be closing those offices “immediately.”

The decision came “after careful consideration of the CDC’s updated guidelines, and in light of current conditions,” a spokesperson said.

“Twitter has made the decision to close our opened offices in New York and San Francisco as well as pause future office reopenings, effective immediately. We’re continuing to closely monitor local conditions and make necessary changes that prioritize the health and safety of our Tweeps,” the spokesperson added.

The company had reopened those offices on July 12. It declined to reveal headcount per office.

The U.S. Centers for Disease Control and Prevention this week recommended that fully vaccinated people begin wearing masks indoors again in places with high COVID transmission rates amid concerns about the highly contagious Delta variant.

Earlier today, TechCrunch’s Brian Heater reported that Google CEO Sundar Pichai announced that the company will require employees to be vaccinated before returning to work on-site. It was part of a larger letter sent to Google/Alphabet staff that also noted the company will be extending its work-from-home policy through October 18 as the Delta variant continues to sweep through the global population.

In a message to TechCrunch, Facebook’s VP of people, Lori Goler, confirmed a similar policy for the social media behemoth.

Amazon also responded to TechCrunch’s inquiry on the matter, noting, “We strongly encourage Amazon employees and contractors to be vaccinated as soon as COVID-19 vaccines are available to them.”