A container assembly including a shield disposed at least partially within a receiving cavity of a receptacle of a lid is disclosed. The shield provides a physical barrier that at least partially covers and blocks an entrance to the receiving cavity to prevent a patient and/or healthcare worker from needle stick injuries. In one embodiment, the shield is adapted to receive a stopper of a collection tube, and the shield is transitionable between a locked position in which the shield is restrained within an open end of the receptacle, and an unlocked position in which the shield is movable within the receiving cavity of the receptacle.
