Juliana Gonçalves - Synopsis

Despite the clear sex-based differences in immune responses to SARS-CoV-2 infection, women in particular life-stages governed by sex hormones, pregnancy and lactation, were excluded from COVID-19 vaccine trials.

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. Our work was the first to demonstrate that breastmilk might convey both immediate (through anti-spike SIgA) and long-lived (via spike-reactive T cells) immune protection to the infant.

The intricate interplay between maternal immune response to SARS-CoV-2 and the transfer of protective factors to the fetus remains unclear. We analyzed mother:neonate dyads from second and third trimester SARS-CoV-2 infections.

Our findings identify a protective role for IgA/IgM-NAbs in gestational SARS-CoV-2 infection and open the possibility that the maternal immune response to SARS-CoV-2 infection might benefit the neonate in two ways, first by skewing maternal immune response towards immediate viral clearance, and second by endowing the neonate with protective mechanisms to curtail horizontal viral transmission in the critical post-natal period, via the priming of IgA/IgM-NAbs to be transferred by the breastmilk and via NK cell expansion in the neonate.