An auto-disable device for use with a sterile single use hypodermic syringe has a barrel adapter (14) configured to attach to the outlet end of the syringe barrel, external to the barrel. A needle hub (12) holding a hypodermic needle (36) is affixed to the barrel adapter, the barrel adapter and the needle hub forming an assembly having a cavity with a passage for the flow of liquid through the device. An elastically-deformable sealing ring (40) and a moveable sealing member (42) having a head (54) and a shaft (52) are positioned in the cavity. The sealing member is moveable within the cavity (38). The ring and moveable sealing member are configured to form a seal, after a single use of the syringe, against a flow of liquid into the syringe for refilling of the syringe.
