Codominant IgG and IgA expression with minimal vaccine mRNA in milk of BNT162b2 vaccinees

Abstract

Lactating women can produce protective antibodies in their milk after vaccination, which has informed antenatal vaccination programs for diseases such as influenza and pertussis. However, whether SARS-CoV-2-specific antibodies are produced in human milk as a result of COVID-19 vaccination is still unclear. In this study, we show that lactating mothers who received the BNT162b2 vaccine secreted SARS-CoV-2-specific IgA and IgG antibodies into milk, with the most significant increase at 3–7 days post-dose 2. Virus-specific IgG titers were stable out to 4–6 weeks after dose 2. In contrast, SARS-CoV-2-specific IgA levels showed substantial decay. Vaccine mRNA was detected in few milk samples (maximum of 2 ng/ml), indicative of minimal transfer. Additionally, infants who consumed post-vaccination human milk had no reported adverse effects up to 28 days post-ingestion. Our results define the safety and efficacy profiles of the vaccine in this demographic and provide initial evidence for protective immunity conferred by milk-borne SARS-CoV-2-specific antibodies. Taken together, our study supports recommendations for uninterrupted breastfeeding subsequent to mRNA vaccination against COVID-19.

Human Milk Antibodies Elicited by BNT162b2 Vaccination have reduced activity against SARS-CoV-2 Variants of Concern

“…However, we detected significantly reduced milk IgA binding to VOCs, including the globally dominant Delta variant, suggesting reduced protection for breastfeeding infants. Additionally, these antibodies were significantly reduced by as early as 4-6 weeks after D2 1 .…”

“…SARS-CoV-2 specific antibody responses are engendered in human milk after BNT162b2 vaccination. 1 However, the emergence of SARS-CoV-2 variants of concern (VOCs) raises questions about the specificity and potential cross-protection mediated by these antibodies. While antibody responses have been extensively studied for vaccinee sera, 2 human milk antibodies – a major contributor to passive immunity for infants – have not been analyzed.…”

Breastfeeding infants receive neutralizing antibodies and cytokines from mothers immunized with a COVID-19 mRNA vaccine

“…Thus far, we identified ten published studies on the immune response to an mRNA-based COVID-19 vaccine in breastmilk of lactating women [9][10][11][12][13][14][15][16][17][18] . Our study adds new information on the vaccine-induced immune response: we show neutralizing ability of antibodies in milk against spike and 4 VOCs that is IgG-driven and high levels of IFNγ in milk.…”

“…As of September 28, 2021, we identified ten published studies on the immune response to an mRNA-based COVID-19 vaccine in breastmilk of lactating women [9][10][11][12][13][14][15][16][17][18] . The number of lactating women included in eight of these studies ranged between 5 and 31; two remaining studies included 84 and 110 lactating women 17,18 .…”

DataSheet_1.docx

“…The function of these antibodies in protection of infants against COVID-19 is not fully understood. In addition, it has recently been shown in a few studies that vaccines mRNA components are not present in milk samples after vaccination (15,16), or were only detected in very low levels in some cases (14), providing reassurance that risks of exposure to the breastfed infant are minimal. Even though the infant receives passive immune protection from milk antibodies after vaccination, there is still significant hesitancy in the lactating population.…”