No vax, no entry: Google and Facebook, two of Silicon Valley’s biggest companies, have both mandated that staffers have received COVID vaccines before they can return to the office.

Google is requiring employees be vaccinated before coming back to the internet giant’s offices in the U.S. in the next few weeks, and in other countries in the coming months, according to a memo from Alphabet and Google CEO Sundar Pichai sent Wednesday.

“Getting vaccinated is one of the most important ways to keep ourselves and our communities healthy in the months ahead,” Pichai wrote in the company-wide email.

Facebook also said that it’s mandating vaccinations for everyone coming to its facilities.

“As our offices reopen, we will be requiring anyone coming to work at any of our U.S. campuses to be vaccinated,” Lori Goler, Facebook’s VP of people, said in a statement Wednesday. The company will implement the policy based on “local conditions and regulations,” she added, and it will have a process for people who can’t be vaccinated for medical or other reasons.

Many other companies and municipal governments are requiring workers to be vaccinated (or undergo regular COVID testing) before they are allowed on-site.

Netflix on Wednesday said the company will require actors and “Zone A” crew members — those who come into close contact with actors — to be vaccinated against COVID-19, in accordance with Hollywood’s new return-to-work protocols. The move comes after Hollywood unions and major studios last week agreed to new protocols giving producers the option to implement mandatory vaccination policies for casts and Zone A crew.

Twitter, for its part, has already required staffers coming back to its offices to show proof of vaccination. On Wednesday, the social network said that based on updated CDC guidelines it is temporarily shutting down its New York and San Francisco offices and has halted return-to-work plans for other locations.

“We’re continuing to closely monitor local conditions and make necessary changes that prioritize the health and safety of our Tweeps,” a Twitter rep said in a statement.