A recent article published in the EClinicalMedicine investigated the safety, immunogenicity and dose-scheduling of Vi-DT typhoid conjugate vaccine among children aged 6-23 months.

This was a single center, observer blind, phase II trial, wherein 277 participants were randomly allocated (2:2:1) to receive one or two doses of Vi-DT or comparator vaccine, between April and July 2018. Anti-Vi IgG titer and geometric mean titers (GMT) were determined at 0, 4, 24 and 28 weeks.

Overall, 114 children received one or two doses of Vi-DT while 57 received comparator. Meanwhile, 112 and 110 participants from single- and two-dose Vi-DT schedules, respectively and 55 from the placebo group were included in the per protocol analysis. The findings confirmed that the safety profile is satisfactory. On the 28-week follow-up, none of the serious adverse events were related to Vi-DT. While the seroconversion rate four weeks after the first dose was 100% in Vi-DT recipients and 7·0% in comparator recipients. Whereas, the seroconversion rate four weeks after the second dose was 98·2% and 21·8% among Vi-DT and comparator groups, respectively. In addition, anti-Vi IgG GMT was significantly higher in Vi-DT than in control group at all post-vaccination visits.

The results suggested that both, single and two doses of Vi-DT vaccine are safe, well tolerated and immunogenic for infants and toddlers, in a moderately endemic setting.

Source: EClinicalMedicine. 2020 Sep 9;27:100540. doi: 10.1016/j.eclinm.2020.100540.