This cohort study assesses the concentration of SARS-CoV-2 antibodies in the breast milk of women who received vaccines for COVID-19 and their correlation with serum antibody levels.

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.

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Flexible-dose pregabalin (150-600 mg/day) significantly reduced pain and anxiety and improved sleep and was generally well tolerated in Latin American patients with neuropathic pain.

Background Transfer of passive and active immunity through human milk is a key aspect in infant protection against infections. Several observational studies demonstrated the passage of postvaccine antibodies through breast milk in women vaccinated against COVID-19, mostly with mRNA-based vaccines, but lacked long-term data. Methods A six-month prospective cohort study was performed to determine SARS-CoV-2 vaccine-induced antibody levels in the breast milk of 33 lactating healthcare workers at different time-points after mRNA BNT162b2 Pfizer-BioNTech COVID-19 vaccination. Moreover, we examined the correlation of SARS-CoV-2 antibody levels between serum and breast milk, adverse events related to vaccination (AErV) and rate of SARS-CoV-2 infections. Results Mothers’ median (IQR) age was 38(36-39) years and 15(10-22) months for infants. SARS-CoV-2 IgG-S1 vaccine-induced levels at different time-points for serum–milk pairs, median (IQR), were: 519(234-937) to 1(0-2.9) arbitrary units (AU)/mL at 2w after first dose, 18,644(9,923-29,264) to 78(33.7-128) AU/mL at 2w, 12,478(6,870-20,801) to 50.4(24.3-104) AU/mL at 4w, 4,094(2,413-8,480) to 19.9(10.8-51.9) AU/mL at 12w, and 1,350(831-2,298) to 8.9(7.8-31.5) at 24w after second dose. We observed a positive correlation of antibody levels between serum and breast milk (Pearson correlation coefficient 0.68), no serious AErV and 2(6%) COVID-19 vaccine breakthrough infections. Conclusions Women vaccinated with Pfizer-BioNTech transmit antibodies into breast milk with a positive correlation with serum levels. Both decreased over time in a 6-month follow-up. Finally, Infants of breastfeeding vaccinated women could be acquiring vaccine antibodies for at least six months after vaccination and serum determination of SARS-CoV-2 IgG-S1 could indicate breastmilk antibody levels.