The present invention is based on the discovery of novel species of the genus Helicobacter that are associated with gastro-esophageal ulceration in pigs. In particular, a novel species, H. cerdo, has been used as a source of antigenic material for the development of vaccine for the treatment of the gastro-esophageal disorders. Most advantageously, the novel Helicobacter and the porcine circoviruses associated with PMWS in pigs are useful for providing combination vaccines whereby immunogens derived from both types of pathogens may be codelivered to the target animal to stimulate the generation of protective antibodies and immunity. The invention, therefore, provides vaccines that are useful for the tratment of gastro-esophageal ulceration and PMWS in porcines. The present invention includes, therefore, multivalent immunogenic compositions and vaccines, multivaccine kits, and combined immunization or vaccination methods which make it possible to use such combined immunization or vaccination programmes.