Valve connector for medical lines for infusion by means of a fluid introducer, comprising: - a tubular body having an inlet end designed for the engagement of an introducer, and an outlet end, - a hollow spike arranged axially into the cavity of the tubular body and having a closed tip facing said inlet end of the tubular body and axially spaced from the latter, said hollow spike being in communication with said outlet end and having a lateral hole spaced from said closed tip for communication with the cavity of said tubular body, and - a sealing member including: - an elastic head having a pre-slit and normally arranged in a closure condition in said inlet end of the tubular body, wherein said pre-slit is closed, said elastic head being axially moveable against said closed tip of the hollow spike, upon insertion of said introducer into said inlet end, for interacting with said closed tip taking an elastically deformed condition of opening of said pre-slit, - an elastic hollow element joined to said head, interposed between said tubular body and said hollow spike and having sealing means (47, 48) in contact with said hollow spike for isolating said lateral hole with respect to the cavity of the tubular body when said head is arranged in the abovementioned undeformed closure condition, said elastic hollow element including an elastic thrust means (36, 45) tending to maintain said head in said closure condition and comprising a base part of said sealing member, having a generally cylindrical axial wall radially spaced from said hollow spike so as to define with the latter an annular chamber; said base part being joined to said elastic hollow element through a generally transverse annular wall which, during the axial movement of said elastic head from said closure condition towards said opening condition, bends inside said annular chamber, wherein said hollow spike has an external annular projection adapted to interact with said sealing means of the elastic hollow element, characterised in that it further includes a substantially inextensible annular member surrounding said elastic hollow element and axially sliding inside said tubular body upon displacement of said elastic head between said closure and opening conditions, in said opening condition said annular member being arranged in a position substantially corresponding to said external annular projection. - a tubular body having an inlet end designed for the engagement of an introducer, and an outlet end, - a hollow spike arranged axially into the cavity of the tubular body and having a closed tip facing said inlet end of the tubular body and axially spaced from the latter, said hollow spike being in communication with said outlet end and having a lateral hole spaced from said closed tip for communication with the cavity of said tubular body, and - a sealing member including: - an elastic head having a pre-slit and normally arranged in a closure condition in said inlet end of the tubular body, wherein said pre-slit is closed, said elastic head being axially moveable against said closed tip of the hollow spike, upon insertion of said introducer into said inlet end, for interacting with said closed tip taking an elastically deformed condition of opening of said pre-slit, - an elastic hollow element joined to said head, interposed between said tubular body and said hollow spike and having sealing means (47, 48) in contact with said hollow spike for isolating said lateral hole with respect to the cavity of the tubular body when said head is arranged in the abovementioned undeformed closure condition, said elastic hollow element including an elastic thrust means (36, 45) tending to maintain said head in said closure condition and comprising a base part of said sealing member, having a generally cylindrical axial wall radially spaced from said hollow spike so as to define with the latter an annular chamber; said base part being joined to said elastic hollow element through a generally transverse annular wall which, during the axial movement of said elastic head from said closure condition towards said opening condition, bends inside said annular chamber, - an elastic head having a pre-slit and normally arranged in a closure condition in said inlet end of the tubular body, wherein said pre-slit is closed, said elastic head being axially moveable against said closed tip of the hollow spike, upon insertion of said introducer into said inlet end, for interacting with said closed tip taking an elastically deformed condition of opening of said pre-slit, - an elastic hollow element joined to said head, interposed between said tubular body and said hollow spike and having sealing means (47, 48) in contact with said hollow spike for isolating said lateral hole with respect to the cavity of the tubular body when said head is arranged in the abovementioned undeformed closure condition, said elastic hollow element including an elastic thrust means (36, 45) tending to maintain said head in said closure condition and comprising a base part of said sealing member, having a generally cylindrical axial wall radially spaced from said hollow spike so as to define with the latter an annular chamber; said base part being joined to said elastic hollow element through a generally transverse annular wall which, during the axial movement of said elastic head from said closure condition towards said opening condition, bends inside said annular chamber,