Closure cap for a container, said closure cap having a cap housing which includes a substantially cylindrical recess which has a top opening and a bottom opening, wherein the bottom opening is closed by means of a pierceable membrane, a plunger which comprises a cover and a substantially cylindrical lateral surface which extends downward from an underside of the cover, wherein the lateral surface engages in the top opening of the recess of the cap housing and has an outside diameter which corresponds substantially to the inside diameter of the recess, and a chamber which is defined by the recess of the cap housing and the plunger which engages in the recess by way of its lateral surface, the plunger and the cap housing being arranged so as to be movable relative to one another between a first, non-active position, in which a bottom edge of the lateral surface is arranged above the membrane of the cap housing and in which the plunger is blocked from being vertically pressed into the recess of the cap housing, and a second, activated position, in which the bottom edge of the lateral surface pierces the membrane, wherein the plunger is movable by means of an essentially rotational movement from the first, non-active position into an intermediate position where the plunger is allowed to be pressed into the recess so as to reach the second, activated position and wherein the plunger is movable from the intermediate position into the second, activated position by means of a translational or a combined rotational and translational movement with reference to the cap housing, characterized in that the plunger has a skirt with a bottom edge which abuts at least in part against a top edge of an outer sleeve of the cap housing, wherein the bottom edge of the skirt and the top edge of the outer sleeve are profiled in such a manner that a rotation of the plunger enables a translational movement of the plunger into the recess of the cap housing. a cap housing which includes a substantially cylindrical recess which has a top opening and a bottom opening, wherein the bottom opening is closed by means of a pierceable membrane, a plunger which comprises a cover and a substantially cylindrical lateral surface which extends downward from an underside of the cover, wherein the lateral surface engages in the top opening of the recess of the cap housing and has an outside diameter which corresponds substantially to the inside diameter of the recess, and a chamber which is defined by the recess of the cap housing and the plunger which engages in the recess by way of its lateral surface, the plunger and the cap housing being arranged so as to be movable relative to one another between a first, non-active position, in which a bottom edge of the lateral surface is arranged above the membrane of the cap housing and in which the plunger is blocked from being vertically pressed into the recess of the cap housing, and a second, activated position, in which the bottom edge of the lateral surface pierces the membrane, wherein the plunger is movable by means of an essentially rotational movement from the first, non-active position into an intermediate position where the plunger is allowed to be pressed into the recess so as to reach the second, activated position and wherein the plunger is movable from the intermediate position into the second, activated position by means of a translational or a combined rotational and translational movement with reference to the cap housing, characterized in that the plunger has a skirt with a bottom edge which abuts at least in part against a top edge of an outer sleeve of the cap housing, wherein the bottom edge of the skirt and the top edge of the outer sleeve are profiled in such a manner that a rotation of the plunger enables a translational movement of the plunger into the recess of the cap housing.