Local and systemic immune responses to combined Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a live oral vaccines after primary immunization and reimmunization

The local and systemic antibody responses elicited following concomitant primary immunization and reimmunization with the live oral attenuated Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a vaccine strains were determined in healthy adult volunteers. A more pronounced serum vibriocidal antibody response was generated after primary immunization compared to reimmunization 2.5 or 3.5 yr later. The seroconversion rate (greater than or equal to 4-fold rise over baseline) was 81% subsequent to primary immunization versus 57% (p = 0.018) and 65% (p = 0.639) upon reimmunization at 2.5 and 3.5 yr, respectively. A similar trend was observed for serum anti-S. typhi lipopolysaccharide (LPS) antibodies. After primary immunization, 48% of subjects manifested a significant rise in coproantibody levels to V. cholerae LPS while 60% did so for cholera toxin (CT). Upon reimmunization, the response rate for LPS ranged from 38% at 2.5 yr to 56% at 3.5 yr (p > 0.05), while that for CT varied from 31% (p = 0.007) to 50% (p = 0.541) at 2.5 and 3.5 yr, respectively. The anti-g. typhi IgA coproantibody response rate was 70% subsequent to primary immunization versus 47% at 2.5 yr (p = 0.021) and 63% at 3.5 yr (p = 0.77). (C) 2000 Published by Elsevier Science Ltd. All rights reserved.