After months of encouraging employees to get vaccinated against COVID-19, companies are beginning to take a harder line and roll out mandates — a dramatic escalation of Corporate America's approach to halting the spread of the virus.

Momentum for vaccine mandates has been building, and President Joe Biden was expected on Thursday to announce a requirement that be vaccinated or be required to submit to regular testing and mitigation requirements. On Wednesday, Google and Facebook became the first two Silicon Valley giants to .

Here are the companies that have announced COVID-19 vaccine requirements for at least some of their employees.

 

GOOGLE

Google CEO Sundar Pichai Wednesday announcing a vaccine requirement for employees who are coming back to the office. The policy would roll out in the United States in the coming weeks and in other regions in the following months as vaccines become more widely available, Pichai said. It's not clear how Google plans to enforce the policy.

 

FACEBOOK

All Facebook employees must get vaccinated before coming back to the office, the company announced Wednesday. "As our offices reopen, we will be requiring anyone coming to work at any of our US campuses to be vaccinated," Lori Goler, Facebook's VP of people said in a statement. "We will have a process for those who cannot be vaccinated for medical or other reasons and will be evaluating our approach in other regions as the situation evolves," she added.

 

NETFLIX

Netflix is requiring COVID-19 vaccines for the casts of all its US productions, as well as the people who come in contact with them, . Last week, Hollywood unions and major studios hammered out return-to-work protocols that include "the option to implement mandatory vaccination policies for casts and crew in Zone A" on a production-by-production basis. "Zone A," consists of the actors and the people who come in close proximity to them.

 

BLACKROCK

BlackRock, the world's largest asset manager, is currently allowing only vaccinated employees to return to the office, a spokesperson for the company said. This decision is a policy adjustment based on employee feedback and an employee survey, the spokesperson said. From September the company will have a "hybrid model," with some vaccinated employees working from the office and others from home, the spokesperson added. The company is planning to share an updated policy for unvaccinated employees later in the summer.

 

MORGAN STANLEY

Morgan Stanley's New York office is staff and clients from entering its headquarters. All employees who work in buildings with a "large employee presence" were required to confirm their vaccination status by July 1, according to a company memo to employees.

 

SAKS FIFTH AVENUE

Luxury department store chain Saks Fifth Avenue is requiring that all employees be vaccinated, the . "We need to be much more office-based," and "the default needs to be our office," CEO Marc Metrick told the Times.

 

THE WASHINGTON POST

All new hires and current employees of the Washington Post will be required to demonstrate proof of full COVID-19 vaccinations, the company's publisher and CEO Fred Ryan said in a memo to employees Tuesday. Ryan stated that the requirement is a "condition of employment" beginning with the publication's return to the office on September 13.

 

ASCENSION HEALTH

Ascension Health announced that it will require COVID-19 vaccinations for all of its employees "for the safety of patients and visitors, our associates, our families and loved ones, and the community," according to from the company. "Ascension will require that all associates be vaccinated against COVID-19, whether or not they provide direct patient care, and whether they work in our sites of care or remotely," the company said in the statement.

 

LYFT

As of August 2, all employees working in Lyft's offices are required to be vaccinated, according to an email Lyft CEO Logan Green sent to staffers that was viewed by CNN Business. In addition, the majority of the company's offices in the United States will now return to the office on February 2, 2022, according to the email, a six-month extension from the company's original return-to-office date. Lyft informed team members several weeks ago that they will be required to submit proof of vaccination in order to return to the office, a spokesperson told CNN Business.

 

TWITTER

Twitter was already requiring employees who returned to the office to show proof of vaccination, but the company on Wednesday took the additional step of closing its offices in New York and San Francisco completely and pause further office reopenings.

The company took the call "after careful consideration of the CDC's updated guidelines, and in light of current conditions," a spokesperson told CNN Business. "We're continuing to closely monitor local conditions and make necessary changes that prioritize the health and safety of our Tweeps."

-- Rishi Iyengar contributed to this report.