A federal appeals court gave the green light for President Joe Biden’s COVID-19 vaccine mandate for large private employers to be implemented as it reversed a previous decision that had put it on hold. The final say over the mandate, which affects some 84 million workers across the United States, will likely rest in the hands of the Supreme Court as opponents immediately filed appeals.

The split ruling by the three-judge panel of the Ohio-based U.S. Court of Appeals for the 6th Circuit overturned a ruling last month by the U.S. Court of Appeals for the Fifth Circuit, in New Orleans, that had blocked the rule. When it was initially unveiled, the mandate from the Occupational Safety and Health Administration (OSHA) was supposed to take effect Jan. 4. On Saturday, the Department of Labor said workers who aren’t vaccinated won’t have to be regularly tested until Feb. 9. The delay is to “account for any uncertainty” that may have been sparked by the legal challenges, the department said.

The rule for large private employers was unveiled shortly after Biden announced in September that his administration would put in place several rules to increase vaccination rates as a way of combating the pandemic that has killed more than 800,000 Americans. OSHA issued the rule regarding large employers last month that required companies with 100 or more employees to require vaccination of most workers. Those who aren’t vaccinated would have to wear masks indoors and undergo weekly COVID-19 tests. The rules, which would not apply to those who work outdoors or only from home, was challenged by several Republican-led states, private businesses and conservative legal groups.