A US federal appeals court Friday reinstated a Biden administration mandate that large companies require Covid-19 vaccines for their employees, after the move was halted in court in November.

President Joe Biden had set a January 4 deadline for companies with more than 100 employees to ensure full vaccination of their workers against Covid-19 -- a rule the administration said would affect more than two-thirds of the country's workforce.

The Friday ruling by the Sixth Circuit Court of Appeals removes an earlier stay, allowing the vaccine order to move ahead, although the matter is likely to head to the Supreme Court.

Judge Jane Stranch did not rule on the ultimate merit of the order, but ruled that it had the potential to be found valid to protect American workers from the coronavirus.

"The Covid-19 pandemic has wreaked havoc across America, leading to the loss of over 800,000 lives, shutting down workplaces and jobs across the country, and threatening our economy," she said.

Therefore the earlier injunction was not lawful, Stranch said.

The ruling contradicts a decision last month from the Fifth Circuit Court of Appeals, which criticized the mandate as "staggeringly overbroad."

Demonstrators march during an anti-vaccine mandate protest in New York on November 20, 2021
Several groups of anti-vaccine and mask mandate protesters gathered outside the SoFi Stadium Sunday as thousands of fans inside watched the Super Bowl. In photo: demonstrators march during an anti-vaccine mandate protest in New York on November 20, 2021. AFP / Yuki IWAMURA

The opposing rulings between the two courts set up a likely appeals challenge at the Supreme Court from the case's petitioners -- which include five strongly Republican states as well as several private companies and religious groups.

Vaccine mandates have a long history in the United States but have generally been established by cities or states.

At issue in this case is the constitutionality of a US president initiating such a sweeping nationwide mandate.

"Vaccination is the single best pathway out of this pandemic," Biden has said of the order.

"Businesses have more power than ever before to accelerate our path out of this pandemic, save lives, and protect our economic recovery."

Mandates announced earlier by several major employers have had impressive results.

As of Friday evening, nearly 85 percent of US adults -- and 72.5 percent of the total population -- had received at least one Covid-19 vaccine dose, according to the Centers for Disease Control and Prevention.