Immunogenicity and Safety Profile of Typhoid Conjugate Vaccine (Vi-DT) Among Nepali Children.

BACKGROUND

Typhoid fever remains a major concern in tropical countries. The availability of an effective vaccine could be an important inclusion to currently available interventions. We reported on our evaluation of the immunogenicity and safety of the typhoid conjugate vaccine (Vi-DT) among Nepali children.

METHODS

The study was an observer blinded, active controlled, randomized phase III clinical trial in children above 6 months and less than 18 years old. Three different lots of Vi-DT(Vi- Diptheria Toxoid); test vaccine and Vi-TT ( Vi-Tetanus Toxoid); comparator vaccines were administered to eligible children. Seroconversion was assessed with blood samples collected at baseline and 4 weeks after the vaccination. A rise of at least 4-fold vi-antibody titer from the baseline was used to indicate positive seroconversion. Data on solicited and unsolicited adverse events were collected.

RESULTS

Four hundred and eighty-eight children participated in the study. Seroconversion rate was 98.61% and 98.36% among participants who received Vi-DT and Vi-TT vaccines respectively. One immediate adverse event was observed only for Vi-DT group. One hundred forty-two and 66 solicited AEs within 7 days were observed with test and comparator vaccine respectively. Unsolicited AEs within 28 days were 125 for test vaccine compared and 77 for the comparator vaccine. Two SAEs were reported which were Not- related to study vaccine.

CONCLUSIONS

The overall seroconversion in Vi DT vaccine was non inferior to the comparator vaccine and the safety profile of the vaccine was good without any life-threatening events.