What question did this study set out to answer?

The main aim was to evaluate the safety and immunogenicity of coadministering WC-rCTB and Ty21a vaccines.

February 8, 2026Journal of Travel Medicine0 citationsOpen Access

Coadministration of oral killed whole-cell recombinant cholera toxin B-subunit vaccine (WC-rCTB) and live salmonella Typhi Ty21a vaccine: a prospective randomized open-label trial

MRMarianna RiekkinenUniversity of Helsinki MTManuela TerrinoniInstitute for Biomedicine SPSari H. PakkanenUniversity of Helsinki

Key Points

The main aim was to evaluate the safety and immunogenicity of coadministering WC-rCTB and Ty21a vaccines.
Randomized 1:1:1 trial involving healthy adults aged 18-65
Groups received either WC-rCTB with Ty21a, WC-rCTB alone, or Ty21a alone
Assessment of antibody-secreting cells and vibriocidal antibodies using ELISPOT and ELISA
Monitoring of adverse events over one month
Stronger rCTB-specific antibody-secreting cell peak responses in the coadministration group (Ch + Ty) compared to WC-rCTB alone (34 vs 94)
Higher serum anti-rCTB IgA and IgG fold-rises in group Ch + Ty compared to group Ch
Vibriocidal fold-rises were similar between the coadministration group and Ty21a alone group
Safety profiles were comparable between all groups

Abstract

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.

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