Acute and memory immune responses following oral cholera vaccination in children are significantly lower than those observed following wild type disease. - GreenMedInfo Summary

Current oral cholera vaccines induce lower protective efficacy and shorter duration of protection against cholera than that afforded by wild type infection, and this difference is most pronounced in young children. Despite this, there are limited data comparing immune responses in children following wild type disease versus vaccination, especially of memory responses associated with long term immunity. Here, we report a comparison of immune responses in young children (2-5 years of age; n=20) and older children (6-17 years of age; n=20) given two doses of a killed oral cholera vaccine containing recombinant cholera toxin B subunit (CtxB) 14 days apart, and compare these responses to those induced in similarly aged children recovering from infection with Vibrio cholerae O1 Ogawa in Bangladesh. We found that the two vaccine groups had comparable vibriocidal and lipopolysaccharide (LPS) specific plasma antibody responses. Vaccinees developed lower levels of IgG memory B cell (MBC) response against CtxB, but no significant MBC responses against LPS. In contrast, children recovering from natural cholera infection developed prominent LPS IgG and IgA MBC responses, as well as CtxB IgG MBC responses. Plasma LPS IgG, IgA and IgM responses, as well as vibriocidal responses, were also significantly higher in children following disease versus vaccination. Our findings suggest that acute and memory immune responses following oral cholera vaccination in children are significantly lower than those observed following wild type disease, especially responses targeting LPS. These findings may explain, in part, the lower efficacy of oral cholera vaccination in children.