Abstract Background Cholera and typhoid fever are often co-endemic, making vaccine coadministration practical. However, due to lack of immunogenicity data, current guidelines advise against coadministration of the oral inactivated whole-cell recombinant cholera toxin B-subunit vaccine (WC-rCTB) and the oral live Salmonella Typhi Ty21a vaccine. Methods Healthy adults (18–65 years) were randomized 1:1:1 to receive WC-rCTB with Ty21a (group Ch + Ty), WC-rCTB alone (group Ch) or Ty21a alone (group Ty). Peripheral blood mononuclear cells (PBMC) were isolated on Days 0, 5 and 7 from all, plus on Days 12 and 14 from WC-rCTB recipients, to assess antibody-secreting cells (ASC) specific to rCTB and to typhoidal O9,12-structures by ELISPOT. Vibriocidal antibodies were assessed, and anti-rCTB IgA/IgG and anti-S. Typhi lipopolysaccharide (LPS) IgA/IgG/IgM were measured by ELISA in Day 0 and 28 ± 3 serum samples. Adverse events (AEs) were recorded during one month. Results The final study population included 63 volunteers, 21 per group. A nonsignificant trend toward stronger rCTB-specific ASC (IgA + IgG + IgM) peak responses were observed in group Ch + Ty compared to group Ch (geometric mean, GM 94 versus 32 ASC/106 PBMC, p = 0.096). Serum anti-rCTB IgA and IgG fold-rises (postvaccination versus prevaccination) were higher in group Ch + Ty than in group Ch (IgA p = 0.039, IgG p = 0.028), whereas vibriocidal fold-rises were comparable between the two groups (p = 0.847). ASC (IgA + IgG + IgM) peak responses to typhoidal O9,12-structures were comparable between groups Ch + Ty and Ty (GM 183 versus 210 ASC/106 PBMC, p = 0.684). Serum anti-S. Typhi LPS IgA, IgG and IgM fold-rises were also similar across Ch + Ty and Ty groups (all p-values ≥0.145). AEs were comparable in single and coadministration groups. Conclusions Coadministration of the oral cholera and typhoid vaccines demonstrated favourable safety and robust immunogenicity for both vaccines, supporting their simultaneous use without spacing precautions.
Riekkinen et al. (Thu,) studied this question.