Table 2.

Classification of patients in four groups regarding fold increase (FI) calculated as anti-S. Typhi IgG levels (U/mL) in post-vaccination (POST) samples divided by IgG levels (U/mL) in pre-vaccination (PRE) samples. n: number of patients.

Group	POST vs. PRE IgG Levels	n
Group 0: Non responders (NR)	</=3 FI and 0–25 U/mL	13
Group 1: Low responders (LR)	>3 FI and 26–55 U/mL	11
Group 2: Intermediate responders (IR)	>3 FI and 56–200 U/mL	12
Group 3: High responders (HR)	>3 FI and >200 U/mL	24