The invention relates to recombinant Kluyveromyces lactis (K. lactis) yeasts which are capable of the highly efficient expression of one or more foreign proteins and are suitable for use as a vaccine for generating a protective immune response against pathogens. The invention provides in particular K. lactis strains for the targeted cloning of foreign antigen-coding nucleic acids into the yeast genome of the K. lactis strain, which is characterized in that the K. lactis strain has integrated expression cassettes for foreign antigens as an alternative or in addition to the KILAC4 locus on the KIURA3-20 locus (KLLA0E22771g) and/or on the KIMET5-1 locus (KLLA0B03938g). The invention further relates to integrative expression vectors and to methods for producing the K. lactis strains of the invention as well as to the use thereof as vaccines.
