Present state of research on cholera vaccine.

Cholera remains today a major health problem in most developing countries. The long-term control of cholera depends on he improvement of hygiene but t his is a distant goal for many countries. The availability of an effective cholera vaccine is thus important for the prevention of cholera in such cou ntries. More than a century after the first attempt to vaccinate against ch olera by FERRAN in Spain, there is still no truly effective cholera vaccine . A bacterial fraction vaccine, referred to as CH? + 2 was prepared by Prof essor A. DODIN. A field trial of this vaccine was carried out in Zaire in 1 983. Significant protection was observed but this vaccine was not evaluated in additional trials. Two other oral cholera vaccines, developed in Sweden and in the USA, were widely experimented on human beings: a combination of cholera toxin B-subunit and inactivated bacterial cells, and a live attenu ated vaccine containing the genetically manipulated Vibrio cholerae O1 stra in CVD 103-HgR. Despite their efficiency as evaluated in field trials (inac tivated vaccine) or on volunteers (live vaccine), these vaccines have drawb acks that may limit their usefulness as practical vaccines. Protection indu ced by he inactivated vaccine was transient in young children, lasting only approximately for six months. One of he safety concerns associated with li ve vaccines is a possible reversion to virulence, Efforts should be continu ed to find a better cholera vaccine. A new vaccine development program base d upon rile hypothesis that immunoglobulin G directed to the O-specific pol ysaccharide of Vibrio cholerae O1 could confer protective immunity to chole ra. This program may lead to the development of a cholera conjugate vaccine to elicit protection in infants.