The present invention relates to a polypeptide construct comprising at least two fragments of an allergen from the Amb a 1 family of allergens from Ambrosia atermisiifolia or variants thereof, wherein the at least two fragments consist of 20 to 50 amino acid residues and wherein at least one fragment is derived from amino acid residues 1 to 50 of the mature allergen and/or at least one fragment is derived from amino acid residues 240 and ending at the C-terminal end of the mature allergen.
