Abstract: An immunogenic composition comprising a deletion mutant of a Clostridioides difficile TcdB toxin (such as TcdB2 or TcdB1) that lacks residues at least from amino acid residue 1769 to amino acid residue 1787 of a wild-type TcdB amino acid sequence or of a protein having high identity thereto, a vaccine comprising the immunogenic composition, a method of stimulating an immune response, a nucleic acid which encodes the amino acid sequence of the deletion mutant, a vector encoding the nucleic acid, and a host cell comprising the vector.