Liquid transfer devices with an integral telescopic vial adapter for use with an infusion liquid container and an initially non-punctured intact discrete injection vial. The integral telescopic vial adapter is configured for initial telescopic snap mounting on a discrete injection vial leaving its injection vial stopper non-punctured until a subsequent compaction for puncturing the injection vial stopper. The integral telescopic vial adapter includes a safety catch mechanism for precluding advertent compaction from a pre-compacted state to a compacted state. The integral telescopic vial adapter includes a clamping arrangement for irreversibly clamping same in its final compacted state.