COVID-19 Neutralizing Antibodies in Breast Milk of Mothers Vaccinated with Three Different Vaccines in Mexico.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused the largest pandemic of this century, and all aspects of this virus are being studied. The efforts to mitigate the negative effects associated with the SARS-CoV-2 pandemic have culminated in the development of several vaccines that are effective and safe for use to the general population. However, one aspect that remains relatively underexplored is the efficacy of different vaccines technologies (mRNA and Adenovirus) in providing passive immunity to infants through breastmilk of vaccinated mothers, and whether the antibodies passed through breast milk are functional. In this study, using a Micro-neutralization assay, we evaluate the presence of neutralizing antibodies in breast milk of lactating mothers vaccinated against SARS-CoV-2 with the Pfizer-BioNtech, Johnson & Johnson (J&J)/Janssen, and CanSino Biologics vaccines. Our results show the greatest neutralizing effect in breast milk from mothers vaccinated with Pfizer, followed by mothers vaccinated with J&J. CanSino vaccinations yielded the breast milk with the least neutralizing effects. The results found in this study relating to the neutralizing capacity of breast milk against SARS-CoV-2 highlight the importance of corresponding health authorities recommending vaccination to lactating mothers and of the continuance of breastfeeding to infants due to the potential health benefits.