Irrespective of the mechanism of protection and the site where circulating serum antibodies neutralize C. difficile, clinical studies and human studies continue to confirm the importance of circulating serum IgG in the protection against CDI.6,61,62 The importance of a mucosally induced IgA response in the protection from CDI remains unclear, and recent studies indicate that systemic IgG responses may be more important in determining clinical outcomes in CDI.5,6,63 Nevertheless, it would be beneficial for a parenteral vaccine to induce both a systemic and a mucosal immune response. Here, CD79A is linked to clostridium difficile infection.