The present invention involves a sterilizable vacuum chamber that provides for sealing a pharmaceutical fluid into a plurality of containers, the chamber comprising a vertically movable container nest holder for holding a container nest bearing a plurality of pharmaceutical containers filled with a pharmaceutical fluid, a container closure nest holder for holding a closure nest bearing a plurality of corresponding container closures and for locating a closure vertically above each corresponding container, a ram for vertically moving the container nests to engage the containers with corresponding closures, and an elastically deformable closure nest restraining element disposed on an opposing side of the closure nest from the container nest. A method is provided for sealing the pharmaceutical fluid into the containers. The method comprises the closure nest restraining element acting on the closure nest to oppose any vertical upward motion of any of the plurality of containers after the engaging of the containers with the closures.