Gonçalves, JJuliano, AMCharepe, NAlenquer, MAthayde, DFerreira, FArcher, MAmorim, MJSerrano, FSoares, H2022-01-212022-01-212021Cell Rep Med. 2021 Dec 21;2(12):100468.http://hdl.handle.net/10400.17/3960In 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.engMAC MED MAFAntibodies, Viral / bloodAntibodies, Viral / immunologyCOVID-19 / immunologyCOVID-19 / prevention & controlCOVID-19 Vaccines / immunology*FemaleHumansImmunity, Maternally-AcquiredImmunoglobulin A, Secretory / immunology*Lactation / immunologyMemory B Cells / immunologyMilk, Human / immunology*SARS-CoV-2 / immunology*Spike Glycoprotein, Coronavirus / immunology*T-Lymphocytes / immunology*mRNA Vaccines / immunologyVaccinationjournal article10.1016/j.xcrm.2021.100468