Since pre-vaccination LPS-specific IgG titers are often used in subject exclusion criteria in many Shigella phase 1 trials, including in the WRSs2/WRSs3 study, surprisingly the 53G CHIM study indicated that, subjects with higher LPS-specific baseline titers of serum IgA, fecal IgA and -memory B cell IgA, but not IgG, did not progress to shigellosis [33]. This evidence concerns the gene CD79A and shigellosis.