The development of a bivalent vaccine against diarrhoeal disease.

The live oral typhoid vaccine Salmonella typhi Ty2la has been successfully used as an effective public health tool for the control of typhoid fever. This paper reviews the progress of one vaccine development programme, which uses this organism as a carrier of the O-antigens of Vibrio cholerae. It is already known that antibodies directed against the O-antigens have been previously demonstrated in animals to be protective against subsequent challenge with virulent organisms. This paper reports that the hybrid orally administrable typhoid/cholera vaccines that have resulted through this programme are immunogenic in humans, and therefore this represents the first significant step towards the development of an effective bivalent typhoid/cholera oral vaccine.