Oral vaccines for cholera control.

Two oral cholera vaccines-inactivated WC/rBS and live CVD 103 HgR-have recently been marketed in Europe. Though the efficacy of the live vaccine is yet to be supported by field trials, the inactivated oral vaccine has shown encouraging results in field trails on different population groups. Since the role of cholera vaccines-including oral vaccines-as a public health tool in epidemic situations is debatable and cholera immunization for travellers will result in a high cost-benefit ratio, endemic cholera remains the main area of their application. The questions raised in the Bangladesh trial about the protective efficacy of WC/rBS vaccine in people infected with the EI Tor biotype, in 'O' blood group people and in those having no previous immunity to cholera have been reconsidered and explored during the recent field trail in South America, with satisfactory results. However, none of these vaccines provide protection against Vibrio cholerae 0139 Bengal. With their widely demonstrated safety and efficacy, oral cholera vaccines are set to make injectable vaccines obsolete.