Secretory IgA and T cells targeting SARS-CoV-2 spike protein are transferred to the breastmilk upon mRNA vaccination

Juliana Gonçalves, A. Margarida Juliano, Nádia Charepe, Marta Alenquer, Diogo Athayde, Filipe Ferreira, Margarida Archer, Maria João Amorim, Fátima Serrano, Helena Soares

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)
29 Downloads (Pure)


In view of the scarcity of data to guide decision making, we evaluated how BNT162b2 and mRNA-1273 vaccines affect the immune response in lactating women and the protective profile of breastmilk. Compared with controls, lactating women had a higher frequency of circulating RBD memory B cells and higher anti-RBD antibody titers but similar neutralizing capacity. We show that upon vaccination, immune transfer to breastmilk occurs through a combination of anti-spike secretory IgA (SIgA) antibodies and spike-reactive T cells. Although we found that the concentration of anti-spike IgA in breastmilk might not be sufficient to directly neutralize SARS-CoV-2, our data suggest that cumulative transfer of IgA might provide the infant with effective neutralization capacity. Our findings put forward the possibility that breastmilk might convey both immediate (through anti-spike SIgA) and long-lived (via spike-reactive T cells) immune protection to the infant. Further studies are needed to address this possibility and to determine the functional profile of spike T cells.

Original languageEnglish
Article number100468
JournalCell Reports Medicine
Issue number12
Publication statusPublished - 21 Dec 2021


  • breastmilk T cells
  • COVID-19
  • lactating women
  • maternal vaccination
  • memory B cells
  • milk-transferred SARS-CoV-2 protection
  • milk-transferred spike-reactive T cells
  • mRNA vaccine
  • plasmablasts
  • spike SIgA


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