On the contrary, SB-1/HVT bivalent vaccines do provide superior protection against MD than either vaccine used alone, through synergistic effects.2,27 Our results demonstrating the potential of the recombinant SB-1 to protect against IBD offers immense opportunities for its use as a bivalent vaccine together with recombinant HVT to induce simultaneous protection against multiple avian diseases, exploiting their enhanced synergistic immune functions. This evidence concerns the gene SHKBP1 and Menkes disease.