LIVE ORAL CHOLERA VACCINE - A PRELIMINARY REVIEW OF ITS PHARMACOLOGY AND CLINICAL POTENTIAL IN PROVIDING PROTECTIVE IMMUNITY AGAINST CHOLERA

The live oral cholera vaccine contains the attenuated strain Vibrio cholerae CVD 103-HgR. This strain is prepared from V. cholerae OI strain 569B (Classical, Inaba) using recombinant DNA technology In countries where cholera is not endemic, serum vibriocidal antibody levels increase greater than or equal to 4-fold in 72 to 100% of recipients of a single oral vaccine dose of 3 to 5 x 10(8) colony-forming units (cfu) and peak approximately 10 days after vaccination. Seroconversion rates are generally lower (16 to 92%) with this dose in adult and child volunteers from countries where cholera is endemic or epidemic, but higher rates of seroconversion (43 to 85%) are observed in these populations when the vaccine close is increased to 5 x 10(9) cfu. Stool excretion of the vaccine strain is minimal. Live oral cholera vaccine prevented diarrhoea in 63 to 100% of volunteers challenged with V cholerae 1 to 24 weeks after vaccine administration and no recipient experienced severe or moderate diarrhoea. The vaccine is well tolerated in both adults and children (aged >2 years) and had a similar tolerability profile as 5 x 10(8) cfu of heat-killed Escherichia coli K-12 in clinical trials. Although field studies are needed to assess its protective activity in areas with endemic or epidemic cholera, live oral cholera vaccine has the potential to offer a practical means of reducing the morbidity and mortality associated with cholera and to provide protection for travellers, professionals and special groups at risk against this disease. Therefore, it should be considered an important advance in the area of cholera immunisation.