Backgrounds:

Promising data on protective immunological response induced by vaccines against SARS-CoV-2 in pregnant and lactating women have already been obtained.

We aimed to study in depth the possibility for the mothers to transfer neutralizing antibodies, induced by the COVID-19 vaccines, to the offsprings both trans placentally and during breastfeeding.

Methods

Eight SARS-CoV-2 vaccinated mothers during pregnancy or breastfeeding and their children were enrolled in the study. Blood samples were collected before SARS-CoV-2 vaccine (ChAdOx1-S and BNT162b2 Vaccines, M0), at delivery (B) and after 3 months from it (T3). Subjects were assigned to 3 study groups: 1) full vaccinated pre-partum (n = 2); 2) partial vaccinated pre partum (n = 4), and 3) fully vaccinated during breastfeeding (n = 2). None of the enrolled subjects were SARS-CoV-2 infected during sampling. Plasma neutralizing antibody (Nab) assay was performed.

Results:

We compared the different groups at each time points (Table 1). In group 1, Nabs in the neonates were detected independently from the level of protection in the mother and the time from the second dose. However, after 3 months from delivery, Nabs waned in both mother and newborn. In group 2, single dose vaccine was not sufficient to elicit Nabs in the mother neither in the newborn. In group 3, we found Nabs in mothers, but not in their children.

Conclusions/Learning Points:

A complete administration of COVID-19 vaccine can elicit a maternal humoral response that effectively transfers to the fetus and neonates. A single dose is not sufficient to confer antibody protection to the newborns. Our preliminary data suggest that Nab activity decrease rapidly in newborn born from fully SARS-CoV-2 vaccinated women, independently from the time of vaccine administration.