IGHA1 and influenza: While no to little induction of total IgA and IgA subclasses against influenza antigens was observed from baseline levels in Spn-colonized participants, the noncolonized group exhibited a median 3-, 1.9-, and 1.7-fold increase in influenza-specific IgA, IgA1, and IgA2 titers, respectively (Supplemental Figure 3A).