The Compositions and Protective Efficacies of the Oral Killed 2 Cholera Vaccines : A Critical Analysis

Manuscript Text File 1 The Compositions and Protective Efficacies of the Oral Killed 2 Cholera Vaccines: A Critical Analysis 3 Shahjahan Kabir 4 Academic Research and Information Management, 754 37 Uppsala, Sweden 5 6 Address correspondence to Shahjahan Kabir, [email protected] 7 ABSTRACT 8 Two cholera vaccines, sold as Shanchol and Dukoral, are currently available. This review 9 presents a critical analysis of protective efficacies of these vaccines. Children under 5 are 10 very vulnerable to the disease, and account for the highest incidence of cholera cases and 11 more than half of the mortality. Both Shanchol and Dukoral are spaced two dose oral 12 vaccines comprising large numbers of killed cholera bacteria. The former contains 13 Vibrio cholerae O1 and O139 cells, and the latter contains V. cholerae O1 cells with the 14 recombinant B subunit of cholera toxin. In a field trial in Kolkata (India), Shanchol, the 15 preferred vaccine, offered protection of 45% in all age groups and only 17% in children 16 under 5 during the first year of surveillance. In a field trial in Peru, two spaced doses of 17 Dukoral offered negative protection in children under 5 and little protection (15%) in 18 vaccinees above 6 during the first year of surveillance. Little is known on Dukoral’s long 19 term protective efficacy. Both the vaccines have questionable composition, using V. 20 cholerae O1 strains isolated in 1947 that have been inactivated by heat and formalin 21 treatment which may denature protein . Immunological studies revealed Dukoral’s 22 reduced and short-lived efficacy, as measured by several immunological endpoints. Various 23 factors such as necessity for multiple doses, poor protection in children under 5, 24 requirement of cold chain, production cost and complex logistics in vaccine delivery greatly 25 reduce the suitability of either of these vaccines for endemic or epidemic cholera control in 26 resource poor settings. 27 CVI Accepts, published online ahead of print on 23 July 2014 Clin. Vaccine Immunol. doi:10.1128/CVI.00378-14 Copyright © 2014, American Society for Microbiology. All Rights Reserved.