Fig. 3: Neutralization of breastmilk and purified breastmilk IgG and IgA.

a SARS-CoV-2 spike bearing pseudovirus neutralization assay on serial dilutions of filtered mRNA-vaccine breastmilk samples collected at 2D7 (n = 10) and of pre-pandemic breastmilk control samples (n = 5). Breastmilk ID₅₀ is indicated in each plot as calculated by the nonlinear regression [inhibitor vs. response] model. Each measurement was carried out in triplicates. Mean and s.d. are indicated for each dilution. Mean and error bar for s.d. are indicated. b Comparison of ID₅₀ values of breastmilk from 2D7 (n = 10) and control samples (n = 5). P values were determined with an unpaired, two-sided Mann−Whitney U-test; P < 0.05 was considered statistically significant. Mean and 95% CI are indicated. c Purified IgG and IgA from breastmilk collected at 2D7 (n = 10) and pre-pandemic control samples (n = 3) (concentration of 50 μg/ml, 33 nM, 13 nM for IgG and IgA, respectively) were subjected to a spike-bearing pseudovirus neutralization assay; percent inhibition was calculated by measuring GFP-positive HEK-293 cells stably expressing hACE2. The number of GFP-positive cells was normalized and converted to a neutralization percentage. Each sample was measured in triplicate, and bar graph plots present mean values ± SEM. Precent inhibition was normalized per 5μg antibody. The horizontal dashed red line indicates 50% inhibition. d Bar plot summarizing the percent inhibition 2D7 breastmilk IgG and IgA (n = 10) in comparison with IgG and IgA from pre-pandemic control samples. The horizontal dashed red line indicates 50% inhibition. Mean and 95% CI are indicated. Source data are provided as a Source Data file.