WASHINGTON, Nov 4 (Reuters) – President Joe Biden will enforce a federal mandate that workers at U.S. companies with at least 100 employees be vaccinated against COVID-19 or be tested weekly starting on Jan. 4, a reprieve to businesses facing labor shortages during the holiday season, U.S. officials said on Thursday.Biden’s separate vaccine requirement for federal contractors has been delayed a month to Jan. 4, officials added, while workers in healthcare facilities and nursing homes participating in the Medicare and Medicaid government healthcare programs will need to get their shots by the same date.The action on the private-sector vaccinations was taken under the U.S. Occupational Safety and Health Administration’s (OSHA) emergency authority over workplace safety, the officials said. The mandate applies to 84.2 million workers at 1.9 million private-sector employers. Another 18.5 million workers for those employers are exempt because they either work remotely or outside all the time, OSHA said.OSHA estimates 31.7 million of those covered workers are unvaccinated and that 60% of employers will require vaccinations, up from 25% today, resulting in another 22.7 million employees getting vaccinated.The Chamber of Commerce, the largest U.S. business group, said Biden’s administration “made some significant adjustments” in the rule that reflect concerns raised by the business community.The mandate is likely to trigger legal challenges and a legal battle hinging upon on the rarely used law on which the action was based and questions over federal power and authority over healthcare practices.The 490-page regulation is known as a Emergency Temporary Standard (ETS). Senate Republicans said they would try to repeal the rule using a law known as the Congressional Review Act.Biden in September unveiled plans to impose the mandate, with his administration seeking to increase vaccination rates amid a dangerous surge in COVID-19 cases and get more people back to work. In numerous meetings with companies and industry groups representing retailers, logistics companies, construction workers, executives asked the administration to delay the implementation deadline after the New Year, citing concerns about worker shortages.Employers will also not be required to provide or pay for tests. The rule offers medical and religious exemptions and it estimates that about 5% of employees will seek and receive religious or medical accommodations.Failure to comply with the mandate will result in an approximately $14,000 fine per violation with a scale that increases with several violations, officials said. They did not offer clarity on whether workers will be fired if they refuse to get the shot or tested.”It is important to understand that there are still so many workers who are not protected and remain at risk from being seriously ill or dying from COVID-19,” said a senior administration official, speaking on condition of anonymity.Biden initially set a deadline for 70% of U.S. adults to get at least one shot by July 4, but the White House missed the deadline as it underestimated the anti-vaccine sentiment among some Americans fueled by right-wing talk show hosts, anti-vaxxers, online disinformation campaigns and resistance from many Republicans.A recalcitrant minority of Americans has refused to accept free vaccinations despite a major rollout and incentive campaign from the administration involving 42,000 pharmacies, dozens of mass vaccination sites, free rides and even free beer.The latest data shows that about 70% of U.S. adults have been fully vaccinated and 80% have received at least one shot. An average of 1,100 Americans are still dying daily from COVID-19, the vast majority of them unvaccinated. COVID-19 has killed more than 745,000 Americans.The Biden administration said it stopped short of requiring the further workplace measures recommended by OSHA and the Centers for Disease Control and Prevention “including distancing, barriers, ventilation and sanitation.””The new emergency temporary standard is well within OSHA’s authority under the law. … There is a well established legal precedent for OSHA’s authority,” a senior administration official said, explaining OSHA’s the legal authority to issue the rule.Along with Biden’s executive order that requires all federal workers and contractors be vaccinated, the administration vaccine rules cover 100 million people, about two-thirds of the U.S. workforce, the White House estimates.The rule for healthcare workers covers 17 million employees across 76,000 healthcare facilities even though a majority of them are already vaccinated, data from the Centers for Medicare and Medicaid Services (CMS) shows.The administration estimates the rule will prevent more than 250,000 hospitalizations and save thousands of lives during the six months after it is implemented.Reporting by Nandita Bose, David Shepardson and Ahmed Aboulenein in Washington and Tom Hals in Wilmington, Delaware; Editing by Will Dunham, Chris Sanders and Shri NavaratnamOur Standards: The Thomson Reuters Trust Principles.