Protein conjugate comprising a protein antigen for generating an immune response against the HER2/neu protein and an immunogenic carrier covalently bonded to said protein antigen, wherein said protein antigen (i) has a sequence segment of 300 or more contiguous amino acids of the amino acid sequence of SEQ ID NO: 1; or (ii) has a variant sequence segment of 300 or more amino acid residues, wherein the amino acid sequence of said variant sequence segment has at least 85% sequence identity to a sequence portion from SEQ ID: 1; or (iii) has a variant sequence segment of 300 or more amino acid residues and has from 1 to 10 substitutions, deletions or additions in said variant sequence segment compared to a sequence segment of 300 or more amino acid residues of the amino acid sequence of SEQ ID NO: 1 or 2.
