The present invention relates to an adaptor (10) for coupling with a vial (1) having a collar (3) closed by a septum (4), said septum having an outer surface directed towards the outside of the vial, the adaptor comprising: - a gripping member (120) for securing the adaptor to the vial, said gripping member being capable of being axially mounted on the collar of said vial and - a pierceable elastomeric piece (30) having at least a part intended to be in contact with the outer surface of the septum when said adaptor is secured on said vial. The invention also relates to an assembly comprising such an adaptor and a vial.
