The Biden administration has postponed a deadline from Dec. 8 to Jan. 4 next year for federal contractors, including defense firms, to have their workers on “covered contracts” be fully vaccinated against COVID-19 unless workers have a religious or health exemption.

“The administration has previously implemented policies requiring millions of federal employees and federal contractors to be fully vaccinated,” the Biden administration said on Nov. 4. “To make it easy for businesses and workers to comply, the administration is announcing today that the deadline for workers to receive their shots will be the same for the OSHA [Occupational Safety and Health Administration] rule, the CMS rule [the Centers for Medicare and Medicaid Services], and the previously-announced federal contractor vaccination requirement. Employees falling under the ETS [Emergency Temporary Standard], CMS, or federal contractor rules will need to have their final vaccination dose – either their second dose of Pfizer or Moderna, or single dose of Johnson & Johnson – by January 4, 2022.”

One crucial question that appears to lack a definitive answer is whether defense contractors who continue to employ the unvaccinated on covered contracts after Jan. 4 will be liable for breach of contract.

“Theoretically, a federal contractor or subcontractor that fails to ensure compliance with all of the new workplace safety requirements pursuant to a covered contractor could be found in breach of contract,” per a blog post last month by the Spencer Fane law firm in Kansas City, Mo. “Violations might also affect a contractor’s past performance ratings.  Depending on the contract’s terms, non-compliance could also reduce the amount paid under the contract or, worse yet, result in the contract’s termination.”

The earlier administration guidance provides a limited exception for an agency head to approve a 60-day exception after Dec. 8 for “urgent, mission-critical need” for covered employees to begin work on a federal contract or at a worksite before becoming fully vaccinated

Sen. Lisa Murkowski (R-Alaska), a member of the Senate Appropriations Committee, said on Nov. 4 that she is backing an effort by congressional Republicans to challenge via the Congressional Review Act (CRA) the White House’s vaccine mandate. Murkowski said she’s received feedback from federal contractors in Alaska that the vaccine mandate will imperil contractor efforts to complete projects on time, as such contractors would have to hire new workers to replace those who refuse vaccinations and leave or are fired.

Top defense contractors, including Lockheed Martin [LMT] and General Dynamics [GD], have said about 75 percent of their employees are fully vaccinated.