Comparative immune response of Typbar TCV® (typhoid conjugate vaccine) in extremes of age: An Indian experience

Typhoid fever is a significant health concern in low- and middle-income countries, with millions of cases and thousands of deaths each year. Typhoid Conjugate Vaccines, such as Typbar TCV®, have been developed to provide longer-lasting protection for young children. This publication includes the readouts from two different studies in Children and elderly: a Comparator Study and Age Extension Study. In the first study, children are included, whereas the latter study also includes elderly subjects. A total of 340 children were enrolled, and a subset received a booster dose of Typbar TCV®, 180 days later. Results established that Typbar TCV® induced significantly higher antibody titer compared to Typhim Vi on days 28 and 90 (<i>p</i> < .001). No significant differences in adverse events were found between the two vaccine arms. Overall, Typbar TCV® was well tolerated, inducing higher anti-Vi-IgG titers than Typhim Vi®, with sustained response over the study period. The booster dose post-6 months in the Typbar TCV® group was significantly less immunogenic compared to a booster at 2 years (<i>p</i> < .001), suggesting a delayed booster might enhance the anamnestic response, a fact confirmed in our previous clinical studies of Typbar TCV®. In the Age Extension study, 300 healthy volunteers, including younger (18-65) and elderly adults (65 and older), received a single dose of Typbar TCV®. The vaccine is reported to be safe and induced similar anti Vi-Ab geometric mean titers (GMTs) in young and elderly adults. Thus, Typbar TCV® was studied effectively from 6 months to above 85 years, which is the upper age limit. CTRI Registration number: CTRI/2016/01/006476, CTRI/2024/06/069638.