[Cholera update and vaccination problems].

Cholera remains an important public health problem. The long-term control of cholera depends on good personal hygiene, uncontaminated water supply and appropriate sewage disposal. However, the improvement of hygiene is distant goal for many countries. Thus the availability of an effective cholera vaccine is important for the prevention of cholera in these countries. Research on new cholera vaccines has mainly focused on oral formulations that stimulate the mucosal secretory immune system. Two oral cholera vaccines were experimented on large scale in human. The first vaccine, containing inactivated bacterial cells and B-subunit of cholera toxin, has been tested in Bangladesh from 1985 to 1989. This vaccine, according to WHO, may prove useful in the stable phase of refugee/displaced person crises, especially when given preventively. The second vaccine is a live attenuated vaccine containing the genetically manipulated Vibrio cholerae O1 strain CVD 103-HgR. Despite its efficacy in adult volunteers, results of a large-scale field trial carried-out in Indonesia for 4 years have shown a surprisingly low protection. Moreover, one of the safety concerns associated with live cholera vaccine is a possible horizontal gene transfer and recombination event leading to reversion to virulence. A new vaccine development program for cholera is based upon the hypothesis that immunoglobulins G directed to the O-specific polysaccharide of Vibrio cholerae O1 could confer protective immunity to cholera by inactivating the inoculum on intestinal mucosal surface. This program may lead to the development of cholera conjugate vaccines to elicit protection in infants.