An injection or access site (1) for medical lines including a tubular body made of molded plastic material (2) within which an elastic sealing element (5) made of thermoplastic material is overmolded within an enlarged end (3) of the tubular body (2) to sealingly close said end. The enlarged end (3) delimits an inner annular flange (4) and is formed with at least one radial through-hole (6) through which the elastic element (5) is overmolded in order to rest axially against the inner annular flange (4) and fill the radial through-hole (6) with an appendage (7), thus locking the sealing element with respect to the tubular body securely against both axial and rotational disengagement, for example during insertion and extraction of an injection needle through the sealing element.
