Exploring the long-term seroprevalence of SARS-CoV-2 antibodies in infants born to women with clinical or laboratory-confirmed COVID-19

Introduction: Infants are at a higher risk of severe illness with COVID-19 infection compared to older children. While COVID-19 vaccination is not recommended for young infants, they can acquire maternally-derived antiSARS-CoV-2 antibodies passively through the placenta and breastmilk. We described the persistence of infectioninduced maternal antibodies in infant circulation at 9-12 months of age. Methodology: This was a cross-sectional study nested within the INTERCOVID multinational cohort study. For each COVID positive pregnant woman, two unmatched consecutive COVID negative pregnant women were enrolled between April and September 2020. Women with a positive PCR test, radiographic signs consistent with COVID-19, or at least 2 predefined symptoms of COVID-19 were considered as COVID positive. For this nested cross-sectional study, all COVID positive and either one of the COVID negative participants recruited from the Aga Khan University, Pakistan were approached 9-12 months after delivery, and maternal and infant sera were collected for antibody detection. Results: Altogether, 83 mothers provided consent, of whom 32 (38.6 %) were COVID positive and 51 (61.4 %) were COVID negative during pregnancy. Anti-SARS-CoV-2 antibodies were present in 13 (41 %) infants born to COVID positive and 19 (39 %) infants born to COVID negative mothers (p = 0.87). The presence of reactive antibodies in infants at follow-up was associated with maternal antibodies at follow-up (OR:9.50, 95 % CI:2.03-44.42; p = 0.004). COVID infection occurred in 3 (6 %) infants born to COVID negative mothers while no infant born to a COVID positive mother had a history of infection (p = 0.27). Conclusion: The presence of reactive anti-SARS-CoV-2 antibodies in infants at 9-12 months of age is associated with maternal seropositivity 9-12 months after delivery rather than maternal infection during pregnancy. Further studies are required to validate these findings and assess whether passive immunity in infants is protective against COVID-19 infection.