Immunological Profile of Typhoid Antibodies among Children and Adults in India

The previous infection group had a higher GMFR of PNT50 (against XBB.1.5)than the no-infection group; 18.67/12.63/9.27 vs. 7.65/10.13/6.91 at D28 and 5.75/5.24/3.50 vs. 1.95/3.06/1.49at D90.For IFN-Gamma, the GMT (mIU/mL) were at 2,079.12/5,046.49/4,088.73vs. 4,721.11/2,741.91/3,645.65 at D28 and 2,234.36/4,437.50/2,726.84vs. 4,206.49/2,314.98/3,712.65 at D90 in those with and without infection.Discussion: Bivalent boosters could stimulate good immune response against the newer Omicron XBB 1.5 variant in all three groups regardless of the doses and with or without adjuvant.However, the magnitude declined significantly 90 days after.It appeared that the magnitude of T-cell responses especially with symptomatic infection appeared to be higher till D90 in the adjuvanted group (3 + CpG).In the event of Omicron surges, the complexity of immune responses in hybrid immunity warrants further exploration.Conclusion: Good safety and immune responses were observed in the context of hybrid immunity and new VOCs, especially XBB.1.5., from bivalent mRNA booster over NDV-HXP-S primary series in all three groups.