The breastfeeding of infants by mothers who are infected with SARS-CoV-2 has become a dramatic healthcare problem. The WHO recommends that infected women should not abandon breastfeeding; however, there is still the risk of contact transmission. Convalescent donor milk may provide a defense against the aforementioned issue and can eliminate the consequences of artificial feeding. Therefore, it is vital to characterize the epitope-specific immunological landscape of human milk from women who recovered from COVID-19. We carried out a comprehensive ELISA-based analysis of blood serum and human milk from maternity patients who had recovered from COVID-19 at different trimesters of pregnancy. It was found that patients predominantly contained SARS-CoV-2 N-protein-specific immunoglobulins and had manifested the antibodies for all the antigens tested in a protein-specific and time-dependent manner. Women who recovered from COVID-19 at trimester I–II showed a noticeable decrease in the number of milk samples with sIgA specific to the N-protein, linear NTD, and RBD-SD1 epitopes, and showed an increase in samples with RBD conformation-dependent sIgA. S-antigens were found to solely induce a sIgA1 response, whereas N-protein sIgA1 and sIgA2 subclasses were involved in 100% and 33% of cases. Overall, the antibody immunological landscape of convalescent donor milk suggests that it may be a potential defense agent against COVID-19 for infants, conferring them with a passive immunity.

The relationship between the incidence of COVID-19 in pregnant women who have had a coronavirus infection at different gestational ages and the health status of paired neonates is of great interest. However, no sufficient convincing data fully reflecting features of subsequent neonatal period, the state of the immune system in this category of children, affecting characteristics of postnatal period have been accumulated. Based on this, it underlies the relevance of the current study aimed at investigating parameters of clinical and immunological state of neonatal health after paired mothers recovered from COVID-19 at different gestational ages. The prospective study included 131 women and 132 children. The main group consisted of women (n = 61) who had COVID-19 during pregnancy and paired newborns (n = 62) at gestational age (GA) of 3741 weeks, the comparison group women without laboratory-confirmed COVID-19 during pregnancy (n = 70) and paired newborns (n = 70) of similar gestational age. While analyzing the anamnesis of the patients, no significant differences in somatic and obstetric-gynecological diseases were found. Analyzing course of pregnancy revealed that low molecular weight heparins were significantly more often applied in the main group. The term and frequency of delivery by caesarean section in pregnant women in the main group did not significant differ from that of the control group. No significant difference in the frequency of causes accounting for the severity of the condition of neonates in paired mothers with COVID-19 at different trimester of gestation was found. Investigating lymphocyte subset composition, neutrophil phagocytic activity, and IgG class antibodies specific to SARS-CoV-2 was carried out. It was found that lymphocyte subset profile in newborns from paired mothers with COVID-19 at different trimesters of gestation differed only in the level of NK cells (CD56+) in children born to mothers recovered from COVID-19 in the first trimester. In this study, in general, no severe perinatal outcomes in newborns from paired mothers with COVID-19 during pregnancy were documented. No cases of moderate or severe maternal COVID-19 were observed. Therefore, further prospective studies are needed to assess an impact of COVID-19 severity on maternal and fetal birth outcomes and clarify optimal management of pregnant women in such cases.