Maternal immunization status and SARS-CoV-2 antibody transfer to neonates at birth.

INTRODUCTION

Following the COVID-19 pandemic, hybrid immunity, arising from a combination of SARS-CoV-2 infection and vaccination, is widespread across populations, yet the dynamics of maternal antibody transfer to neonates in this context are not fully characterized.

METHODS

We conducted a cohort study of 117 pregnant women, assessing IgG antibodies against SARS-CoV-2 nucleoprotein and receptor-binding domain (RBD) in maternal, umbilical cord, and neonatal blood at delivery.

RESULTS

Using ELISA and pseudo virus neutralization assays, we found that 95% of mothers had detectable IgG, with 87% of neonates acquiring antibodies trans placentally. Hybrid immunity, detected in 65.5% of mothers, was associated with higher anti-RBD IgG levels in newborns compared to natural or vaccination-induced immunity alone. Neutralizing antibodies correlated positively with IgG titers, with umbilical cord samples showing the highest neutralization capacity.

DISCUSSION: These findings suggest that combined natural infection and vaccination in mothers enhance passive immunity in neonates, potentially improving early-life protection against SARS-CoV-2.