In a recent study published in PLOS ONE Journal, researchers evaluated the efficacy of transplacental transfer of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to infants from mothers receiving coronavirus disease 2019 (COVID-19) vaccines before and after the birth of the infant.
Study: Maternal transfer of IgA and IgG SARS-CoV-2 specific antibodies transplacentally and via breast milk feeding. Image Credit: OnjiraLeibe/Shutterstock.com
Background
Breastfeeding is strongly advocated, given its known health benefits, especially those associated with neonatal immunity during the initial months, when infants are highly prone to develop infections.
COVID-19 vaccine doses are available only for infants aged ≥6.0 months in most nations. Transplacental antibody transfer from mothers to their infants could protect neonates against adverse COVID-19 outcomes.
Pregnant women are advised to get vaccinated against COVID-19; however, many are either reluctant or choose to receive vaccines in the postpartum period.
Studies have reported on humoral immunity against SARS-CoV-2 in human milk; however, the extent of passive immune protection in infants is limited.
About the study
In the present cross-sectional study, researchers investigated the appropriate timing of maternal COVID-19 vaccination to provide effective humoral anti-SARS-CoV-2 immunity to infants.
The study comprised mother/neonate pairs recruited at the medical center of Maryland University through oral communication.
The pairs were divided into two study groups: mothers receiving COVID-19 vaccines before infant birth and practicing breastfeeding and those who practiced breastfeeding and received COVID-19 vaccines after the infant's birth.
COVID-19 vaccines administered included two-dose BNT162b2 (Pfizer-BioNTech) vaccines or messenger ribonucleic acid (mRNA)-123 (Moderna) vaccines.
Samples of maternal blood, human milk, neonatal blood, neonatal nasal mucosal, and neonatal stool were obtained and examined for anti-SARS-CoV-2 spike (S) protein immunoglobulin G (IgG) and IgA antibodies using enzyme-linked immunosorbent assays (ELISA).
The team excluded mother/neonate pairs exhibiting anti-SARS-CoV-2 nucleocapsid (N) protein IgG titers from the analysis. Infants consumed breast milk via breastfeeding or bottle feeding of expressed breast milk.
Linear regression (continuous decay) modeling was performed to calculate the half-lives (t1/2) for nasal and serological antibody titers.
Results
In total, 31 mother/neonate pairs' data were analyzed, of which 18 pairs and 13 pairs belonged to the groups of antepartum-vaccinated mothers and postpartum-vaccinated mothers, respectively. The median values (years) of antepartum-vaccinated and postpartum-vaccinated mothers were 33.0 and 34.0 years, respectively.
The median values for the age of gestation among mothers receiving antepartum and postpartum COVID-19 vaccinations were 40.0 weeks and 39 weeks, respectively, and for infant age (days) at sampling in the corresponding groups, were 167 and 353, respectively.
Antepartum and postpartum COVID-19 vaccinations were administered 161 days before and 146 days after birth, respectively.
No pairs displayed anti-SARS-CoV-2 nucleocapsid IgG titers; therefore, none had recent SARS-CoV-2 infection.
Human milk-fed neonates showed anti-S IgG titers only in the case of maternal antepartum COVID-19 vaccination (100.0% and 0.0% for mothers receiving antepartum vaccinations and postpartum vaccinations, respectively).
Only human milk-fed neonates of antepartum-vaccinated mothers showed nasal mucosal anti-S IgG titers (89.0% and 0.0% for antepartum and postpartum periods, respectively).
No infants of either of the study groups displayed serological anti-S IgA titers. Surprisingly, 33.0% of infants born to mothers receiving antepartum COVID-19 vaccinations had high nasal anti-S IgA titers (33.0% and 0.0% for the antepartum and postpartum periods, respectively).
Among infants of antepartum-vaccinated mothers, the t1/2 value of vertically transferred serological anti-S IgG antibodies from the mother to her infant was 70.0 days. The serological and nasal anti-S IgG endpoint titers showed direct correlations.
The serological and nasal anti-SARS-CoV-2 IgG titers were reduced with advancing infant age. The t1/2 values for serological and nasal maternal anti-S IgG antibody titers in infants were 57 days and 84 days, respectively.
Conclusions
Based on the study findings, antepartum COVID-19 vaccinations and subsequent breastfeeding most effectively confer local-level and systemic-level humoral immune protection against SARS-CoV-2 in neonates.
The high anti-SARS-CoV-2 IgA nasal titers presence in infants underscores the probable importance of breast milk feeding early in life for the vertical transfer of mucosal IgA antibodies to protect infants against respiratory pathogens.
Notably, IgG was detected in all antepartum group breast milk-fed infants (the oldest at 11.0 months), whereas none were detected in postpartum group infants (as young as one month).
Expectant mothers should consider being vaccinated in the antepartum period and consider breast milk feeding for optimal transfer of systemic and mucosal antibodies to their infants.
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