An immunogenic variant Protein A (SpA) comprising: (a) amino acid substitutions in a V H 3-binding sub-domain of SpA domain E, D, A, B or C that disrupt or decrease binding to V H 3, wherein the SpA variant comprises a domain E comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 33 and 34 of SEQ ID NO: 3; a domain D comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 36 and 37 of SEQ ID NO: 2; a domain A comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 4; a domain B comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 6; and/or a domain C comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 5, and (b) amino acid substitutions in an IgG Fc binding sub-domain of SpA domain E, D, A, B or C that disrupt or decrease binding to IgG Fc, wherein the SpA variant comprises a domain E comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 6 and 7 of SEQ ID NO: 3; a domain D comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 9 and 10 of SEQ ID NO: 2; a domain A comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 4; a domain B comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 6; and/or a domain C comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 5. (a) amino acid substitutions in a V H 3-binding sub-domain of SpA domain E, D, A, B or C that disrupt or decrease binding to V H 3, wherein the SpA variant comprises a domain E comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 33 and 34 of SEQ ID NO: 3; a domain D comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 36 and 37 of SEQ ID NO: 2; a domain A comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 4; a domain B comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 6; and/or a domain C comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 34 and 35 of SEQ ID NO: 5, and (b) amino acid substitutions in an IgG Fc binding sub-domain of SpA domain E, D, A, B or C that disrupt or decrease binding to IgG Fc, wherein the SpA variant comprises a domain E comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 6 and 7 of SEQ ID NO: 3; a domain D comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 9 and 10 of SEQ ID NO: 2; a domain A comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 4; a domain B comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 6; and/or a domain C comprising an amino acid substitution at each of the amino acid positions corresponding to amino acid positions 7 and 8 of SEQ ID NO: 5.