In some highly immunized countries with long history of pertussis vaccination (The Netherlands, Finland, Poland, USA, France, Great Britain) differences in the DNA patterns and ptxS1 and prn alleles present in B. pertussis strains used for production of pertussis component in the DTP vaccine, in comparison to strains presently isolated from clinical materials have been found. Studies on efficacy of whole-cell and acellular pertussis vaccines in elimination of B. pertussis strains harbouring different gene variants in a particular country might indicate a need for a change of B. pertussis strains used for production of the vaccine against pertussis.