Table 2.

Distribution of shigellosis cases and non-cases from the CHIM study population according to S. sonnei LPS serum IgG threshold at 28 days post-second vaccination

	Shigellosis outcome
Threshold	Cases	Non-cases	Sensitivity	Specificity
<396 EU/mL	22	22	81.5%
≥396 EU/mL	5	11		33.3%
Total	27	33

396 EU/mL in the current GSK Vaccines Institute for Global Health enzyme-linked immunosorbent assay used is equivalent to the 1:1600 titer in the Tel Aviv University assay¹³.

CHIM controlled human infection model, LPS lipopolysaccharide, IgG immunoglobulin G, EU enzyme-linked immunosorbent assay unit.

Sensitivity was calculated as the number of participants with shigellosis and S. sonnei LPS serum IgG levels below the threshold over the total number of participants with shigellosis. Specificity was defined as the number of participants without shigellosis and S. sonnei LPS serum IgG levels equal to or above the threshold over the total number of participants without shigellosis.