Breast milk of those vaccinated against COVID-19 may protect infants

A new study from the University of Florida provides more evidence that the breast milk of people vaccinated against COVID-19 provides protection to infants too young to receive the vaccine.

Vaccination during pregnancy is known to generate functional anti-spike IgG antibodies in maternal circulation that are detectable in umbilical cord blood at birth and can protect the infant from COVID-19 [4,5,6,7]. Further, recent studies have demonstrated that COVID-19 infection, as well as vaccination against COVID-19, induces secretion of neutralizing SARS-CoV-2 IgA and IgG in human milk (HM) [8,9,10,11,12,13,14,15,16].

However, little is known about the transfer of neutralizing HM antibodies to breastfeeding infants.

HM has antimicrobial properties, evidenced by the decreased rate of infections and hospitalization among breastfeeding infants [17]. This can be attributed to molecules with immuno-protective functions within HM: immunoglobulins, lactoferrin, oligosaccharides, and cytokines, to name a few [18].

HM antibodies, in particular, sIgA, prevent the entry of microorganisms into the tissue by decreasing surface colonization and dampening penetration of potentially harmful organisms [19].

SARS-CoV-2 relies on its main receptor, angiotensin-converting enzyme 2 (ACE2), to enter cells, which is abundantly present in the human epithelia of the lung, small intestine, and colon [20, 21].

Reports have shown that a notable proportion of patients with COVID-19 develop gastrointestinal symptoms and nearly half of patients have detectable SARS-CoV-2 RNA in their fecal samples [22, 23].

To protect against SARS-CoV-2 infection, the immune system must mount a robust and specific response. In addition to SARS-CoV-2-specific antibody concentration, antibody specificity, affinity, and neutralizing capacity are also necessary to elicit a proper immune response.

As such, we hypothesize that there is a transfer of neutralizing HM SARS-CoV-2 specific IgA and IgG to the intestinal tract of breast-fed infants that can protect them from COVID-19 infection. Together our results provide interesting insight into the relationship between the durability of maternal antibodies subsequent to vaccination, and the potential protection of breastfed infants.

reference link : https://www.nature.com/articles/s41372-022-01581-5