Fig. 4. Anti–receptor-binding domain (RBD) immunoglobulin (Ig)G and IgA levels in infant stool are higher in infants of mothers who reported side effects after vaccination. Levels of anti-RBD IgG (A) and anti-RBD IgA (B) in stool samples obtained from infants (n=24) of vaccinated mothers. Horizontal dotted lines indicate positive cutoff values. Comparison of levels of anti-RBD IgG (C) and anti-RBD IgA (D) between stool obtained from infants of mothers who reported no side effects and those who reported vaccine-related side effects. Differences in levels of infant stool anti-RBD antibodies stratified by the presence of maternal side effects were assessed with independent t tests. OD, optical density.

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