Tens of millions of Americans who work at companies with 100 or more employees will need to be vaccinated against COVID-19 by Jan. 4 or get tested for the virus weekly.
The new government rules issued by the Department of Labor's Occupational Safety and Health Administration (OSHA) take effect Thursday.
OSHA says companies that fail to comply could face penalties of nearly $14,000 per violation.
The new requirements were first previewed by President Joe Biden in September as part of a six-pronged plan to combat COVID-19 in the fall and winter months.
They will apply to about 84 million workers at medium and large businesses. It is not clear how many of those employees are unvaccinated.
A senior administration official says the agency would target companies if it gets complaints.
Also on Thursday, the White House announced that the Centers for Medicare & Medicaid Services is issuing a rule that will require workers at facilities who receive Medicare and Medicaid funding to be vaccinated against the virus. That mandate will also go into effect on Jan. 4, and it covers an additional 700,000 workers.
As of Thursday, the Centers for Disease Control and Prevention reports that 80% of adults and 67% of the entire U.S. population has gotten at least one dose of a COVID-19 vaccine.
