PCT No. PCT/SE96/00570 Sec. 371 Date Jan. 5, 1998 Sec. 102(e) Date Jan. 5, 1998 PCT Filed May 2, 1996 PCT Pub. No. WO96/34893 PCT Pub. Date Nov. 7, 1996Hybrid molecules between heat-labile enterotoxin B subunit (LTB) and cholera toxin B subunit (CTB) are disclosed. Such a hybrid molecule comprises an amino-acid sequence which is composed of the amino-acid sequence of mature CTB in which such amino-acid residues are substituted with the corresponding amino-acid residues of mature LTB which impart LTB-specific epitope characteristics to said immunogenic mature CTB, or vice versa. In addition, a structural gene coding for such a hybrid molecule, a plasmid containing such a structural gene, and an immunogenic protein comprising such a hybrid molecule and optionally an immunoreactive amino-acid sequence of a prokaryotic or eukaryotic cell or a virus, are disclosed. Disclosed is also a vaccine, e.g. against enterotoxin-induced illness, comprising such an immunogenic protein, and a method of preventing or treating enterotoxin-induced illness in an individual.