Quantification of specific antibodies against SARS-CoV-2 in breast milk of lactating women vaccinated with an mRNA vaccine

Abstract

INTRODUCTION The recent approval of vaccines against COVID–19 has generated great concern among breastfeeding women, since these patients were excluded from vaccination clinical trials. The present study aimed to analyze the levels of specific SARS–CoV–2 antibodies in breast milk of mRNA–vaccinated women across time and their correlation with serum antibody levels. METHODS Prospective study including lactating women aged over 18 who were vaccinated against SARS–CoV–2 with the Pfizer–BioNTech® COVID–19 vaccine (BNT162b2). Paired serum and breast milk samples were simultaneously taken from each participant at three timepoints after receiving the vaccine: 2 weeks after 1st dose, 2 weeks after 2nd dose and 4 weeks after 2nd dose (Timepoints 1, 2 and 3, respectively). Levels of IgG antibodies against the spike protein (S1 subunit) were determined for each sample (Architect, Abbott®). RESULTS We collected and analyzed 52 serum and 52 milk samples from the first 18 study participants. Median (interquartile range) IgG(S1) levels for serum – milk pairs at each timepoint were 410 (208-606) – 1.7 (0-2.9) AU/ml at Timepoint 1, 11505 (8933 – 21184) – 52.2 (34.1–113) at Timepoint 2 and 8311 (5578–17419) – 41.7 (24.8–75.3) at Timepoint 3. Pearson′s correlation coefficient between breast milk and serum IgG(S1) levels was 0.71. No major adverse reactions were observed in mothers or infants. CONCLUSIONS Breast milk from women vaccinated with mRNA–based Pfizer–BioNTech® vaccine contains specific anti–SARS–CoV–2 IgG(S1) antibodies, with levels increasing considerably after second dose. IgG(S1) levels in breast milk are positively correlated with corresponding serum levels.

Systematic review of the safety, immunogenicity, and effectiveness of COVID‐19 vaccines in pregnant and lactating individuals and their infants

“…Esteve-Paula et al 23 18/18 (IgG-S1) 18/18 (IgG-S1) N/A Taken together, the studies from Friedman et al 27 and Esteve-Palau et al 23 suggest that peak antibody titers may occur as early as 7 days after the second dose and last as long as 28 days after the second dose.…”

“…Eight studies noted an increase in IgG, IgM, and/or IgA in the sera of pregnant and lactating individuals after vaccination. 16,18,[22][23][24][25][26][27] Gray et al 18 observed that IgM and IgA titers were strongly induced after the first dose in 115 pregnant and lactating individuals. IgG was robustly induced after both doses, and by 2 weeks after the second vaccine, the dominant serum antibody response was IgG.…”

COVID-19 mRNA vaccine and antibody response in lactating women: a prospective cohort study

“…Pregnant and lactating women were excluded from initial clinical trials for anti-SARS-CoV-2 vaccination, and many concerns, especially safety issues, arose related to vaccination in this specific population. To our knowledge, only a few studies have addressed this topic [12][13][14][15]. To date, there are no robust studies regarding the safety and efficiency of vaccination in lactating women.…”

Anti-Sars-Cov-2 IgA And IgG In Human Milk After Vaccination Is Dependent On Vaccine Type And Previous Sars-Cov-2 Exposure: A Longitudinal Study

“…However, information on their dynamics after vaccination remains limited. While accumulating data are being provided for mRNA-based vaccines 12,19,20 , no information is available for the adenovirus-based vaccine (AstraZeneca).…”