New pertussis toxin (PT) mutants are described being immunologically active and having reduced or no toxicity, characterized in that at least one of the aminoacid residues Glu129, Asp11, Trp26, Arg9, Phe50, Asp1, Arg13, Tyr130, Gly86, Ile88, Tyr89, Tyr8, Gly 44, Thr53 and Gly80 or subunit's 1 aminoacid sequence is deleted and substituted by a different aminoacid residue selected in the group of natural aminoacids; Bordetella strains capable of providing and secreting said PT mutants and means and methods for obtaining them are also described.The Bordetella strains and the PT mutants produced by them are particularly suitable for the preparation of effective cellular and acellular antipertussis vaccines.(FIG. 1)