Figure 3.

Lactating women have higher frequencies of RBD-reactive memory B cells and anti-RBD antibodies in circulation

(A) Gating strategy for CD3⁻CD19⁺IgD⁻ B cells in skim milk after first (prime) and second (boost) vaccine doses.

(B) Gating strategy for circulating RBD-reactive CD3⁻CD19⁺IgD⁻CD20⁻CD27⁺ plasmablasts and CD3⁻CD19⁺IgD⁻CD20⁺CD27⁺ memory B cells.

(C) Cumulative frequency of circulating total B cells (top left), RBD-reactive B cells (top right), plasmablasts (bottom left), and memory B cells (bottom right) after first (prime) and second (boost) vaccine doses for nursing and after the second (boost) vaccine dose for controls.

(D) Endpoint titers for anti-RBD IgG, IgA, and IgM in skim milk and plasma of nursing women and in plasma of controls. nd, non-detectable.

(E) Correlation between anti-spike IgG and neutralization titers with the frequency of RBD-reactive B cells upon vaccine boosting.

(F) Correlation between anti-spike IgG and neutralization titers (NT₅₀) and the frequency of RBD-reactive memory B cells upon vaccine boosting.

Circles, Pfizer vaccine; squares, Moderna vaccine. n = 23 nursing women and n = 22 controls. p values determined using non-parametric paired Wilcoxon test, t test, and Man-Whitney test as appropriate. Pearson and Spearman correlations. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, and ∗∗∗∗p < 0.0001; ns, not significant.