Serological survey for IgG antibodies against SARS-CoV-2 from newborns and their mothers

This serological survey, conducted in five Brazilian municipalities, evaluated the use of dried blood spots (DBS), obtained from newborns and their mothers, to detect SARS-CoV-2 IgG antibodies. DBS were obtained from 4,803 neonates aged up to seven days and their mothers, both asymptomatic, at public health care clinics during newborn screening. DBS were processed by ELISA to detect IgG antibodies against SARS-CoV-2 nucleocapsid antigen. Mothers of seropositive neonates were interviewed about sociodemographic characteristics and clinical and laboratory antecedents. Non-satisfactory samples, dyads with incomplete data, and vaccinated mothers were excluded. Of the 1,917 DBS dyads samples analyzed, 14.7% of neonates showed IgG antibodies against SARS-CoV-2. Among seropositive neonates, 73.2% of their mothers were also seropositive. More than half of the mothers with seropositive neonates denied clinical or laboratory suspicion of COVID-19 during pregnancy. Suspicion occurred in the third trimester for 24.6% of the mothers. This study tested an innovative strategy to improve the understanding of COVID-19 antibody dynamics during pregnancy and suggests the feasibility of a universal serological survey in puerperal women and neonates.