Figure 1.

mRNA vaccines induce production of SIgA into the breastmilk early upon first dose administration

(A) Anti-spike IgG, IgA, and IgM in plasma and skim milk of breastfeeding women (n = 23), measured by absorbance at 450 nm (OD₄₅₀).

(B) Correlation between anti-spike IgG, IgA, and IgM and donor’s age in years.

(C) Correlation between anti-spike IgA in plasma and skim milk.

(D) Correlation between anti-spike IgA and IgG in skim milk.

(E) Donor-matched analysis between anti-spike and anti-RBD SIgA in skim milk.

(F) Correlation between anti-spike IgA and SIgA in skim milk.

(G) Endpoint titers for anti-RBD antibodies in skim milk (IgA) and plasma (IgG, IgA, and IgM).

(H) Neutralization curves for plasma and skim milk.

Orange, plasma; purple, skim milk. Circles, Pfizer; squares, Moderna. Dashed line, assay cutoff. n = 23 nursing women and n = 22 controls. p values determined using ANOVA, post hoc Turkey and Friedman tests, or post hoc Dunn test when comparing three groups and using parametric paired t test and non-parametric paired Wilcoxon test as appropriate. Pearson and Spearman correlations. ∗∗p < 0.01, ∗∗∗p < 0.001, and ∗∗∗∗p < 0.0001; ns, not significant.