A vial adapter modular assembly (10) including a bag spike port (12) connectable to an output port (16) of a bag (18), a vial port (20) connectable to a vial, and an exit port (24), characterised by a lumen (32) having a vial port flow opening (36) in fluid communication with the vial port (20), and a plunger element (34) that slides in the lumen (32) between a non-blocking position and a blocking position, wherein in the non-blocking position, the plunger element (34) does not block the vial port flow opening (36) and permits fluid flow between the bag spike port (12) and the vial port (20), and wherein in the blocking position, the plunger element (34) blocks the vial port flow opening (36) and blocks fluid flow between the bag spike port (12) and the vial port (20).
