Cholera remains an important public health problem.
Epidemic cholera is caused by two Vibrio cholerae serotypes O1 and O139. The disease is spread through contaminated water. According to information reported to the World Health Organization in 1999, nearly 8,500 people died and another 223,000 were sickened with cholera worldwide. In addition to the conjugation methods, also claimed in the invention are methods of immunization against V. cholerae O139 using the conjugates of the invention. The inventors have shown that the conjugates of the invention elicited in mice high levels of serum antibodies to CPS, a surface antigen of Vibrio cholerae O139, that have vibriocidal activity.