FIG 6.

Serological trends associated with reduced disease severity. (A and B) Associations between IpaB- and VirG-specific serum IgG titers (A) and between SBA and OPKA titers (B) in EcSf2a-2 vaccine recipients and nonvaccinated controls prior to challenge. (C and D) Serological trends of IpaB and SBA titers (C) and VirG and OPKA titers (D) associated with disease severity. Gray circles represent individuals who remained healthy or had mild symptoms postchallenge (n = 14), and red circles represent those who experienced moderate to severe disease (n = 14). Dotted lines represent IpaB-specific IgG titers of ≥1,500 EU ml⁻¹, VirG titers of ≥700 EU ml⁻¹, and SBA and OPKA endpoint titers of ≥200.