Sources said the management and operations contractor for the National Nuclear Security Administration’s two big nuclear-weapons production sites suspended its employee COVID-19 vaccine mandate this week after a federal judge in Georgia blocked the Biden administration’s mandate for all federal contractors.

A pair of other nuclear-weapon sites, however, said they would keep mandates in place.

The Bechtel National-led Consolidated Nuclear Security (CNS) suspended the mandate for employees at the Pantex Plant in Amarillo, Texas, and the Y-12 National Security Complex in Oak Ridge, Tenn., following Tuesday’s preliminary injunction in the U.S. District Court for the Southern District of Georgia. The injunction blocks enforcement of the vaccine mandate while the court case proceeds.

A CNS spokesperson had no immediate comment on Friday.

Most prime contractors at Department of Energy defense-nuclear sites had had their contracts modified to include a vaccine mandate well before this week’s decision, after which the Safer Federal Workforce Task Force updated its guidance to agencies to clarify that the government will no longer enforce vaccine mandates arising from Biden’s executive order.

That means the Department of Energy’s National Nuclear Security Administration (NNSA) does not have to modify contracts to suspend existing mandates tied to the order, a spokesperson at agency headquarters in Washington wrote Friday in an email. “[T]he direction to contractors is self-executing and the contracts need not be modified,” the spokesperson wrote.

A spokesperson for the office of Secretary of Energy Jennifer Granholm and spokespersons four of the six other major NNSA site management and operations contractors did not comment about their plans, if any, to alter or remove COVID-19 vaccine requirements inserted into contracts earlier this autumn.

The Sandia National Laboratories and the Nevada National Security Site affirmed at deadline Friday that their vaccine mandates would remain in place.

“The Sandia vaccination policy will remain in place, and the labs will continue to encourage employees to vaccinate by the Jan. 18, 2022, vaccine deadline,” a labs spokesperson wrote in an email.

At the Nevada National Security Site, management prime Mission Support and Test Services’ “vaccination policy will remain in place and the company will continue to encourage employees to vaccinate by the Jan. 4, 2022, vaccine deadline,” a test-site spokesperson wrote in an email. The Nevada spokesperson added that the site recently took “its first action with regard to employee non-compliance” with the mandate, but declined to comment further.

Several DoE defense-nuclear sites that share vaccination data have reported vaccination rates much higher than the national average. The NNSA nuclear weapons laboratories all claimed vaccination rates of 90% or more, as of Friday morning.

At Y-12 and Pantex, thousands of workers became fully vaccinated between Sept. 10, a day after Biden’s order, and this week. At Pantex there were 3,800 fully vaccinated as of Friday and at Y-12, 7,170 were fully vaccinated. That’s up about 1,800 and 2,800, respectively, since the onset of the mandate.

At DoE nuclear sites, deadlines to get vaccinated or get fired, unless exempted from the now-enjoined mandate for religious or medical reasons, ranged from Nov. 30 to Jan. 18. The Biden administration’s Safer Federal Worker Task Force moved the deadline to Jan. 18 from Dec. 8 on Nov. 4.

Though it is the exception and not the rule, contractors can and have adopted their own vaccine mandates. Triad National Security, the NNSA’s operations contractor for the Los Alamos National Laboratory, put a vaccine mandate in place in August, before Biden’s executive order came down. That mandate has so far survived court challenges.

A version of this story first appeared in Defense Daily affiliate publication Nuclear Security & Deterrence Monitor.