394 - Infant immunity following maternal COVID-19 Booster vaccination in pregnancy/postpartum or COVID disease in pregnancy

Publication Number: 2383.394

Rupsa C. Boelig, Thomas Jefferson University, Garnet Valley, PA, United States; Elke S. Bergmann-Leitner, Uniformed Services University of the Health Sciences F. Edward Hebert School of Medicine, Silver Spring, MD, United States; Wathsala WIJAYALATH, Naval Medical Research Command/Henry M Jackson Foundation, Silver Spring, MD, United States; Zubair H. Aghai, Nemours Children's Hospital, Philadelphia, PA, United States

Background: There is limited data on longitudinal infant immunity following maternal COVID booster dose in pregnancy, and the implications of receiving COVID booster dose received in pregnancy vs postpartum vs COVID disease. Updated studies since the original pandemic are needed to take into consideration basal immunity.

Objective: We aimed to characterize the isotypes of COVID related antibodies identified in breastmilk and infant serum at birth and 30days of life following maternal COVID booster vaccination or COVID disease.

Design/Methods: This is a longitudinal cohort of patients in 2022-2023 who either received COVID mRNA booster in pregnancy, postpartum, or had COVID in pregnancy but did not receive COVID booster. Cordblood was collected at delivery; breastmilk and infant serum were collected 30 days postpartum. MesoScale multiplex platform was used to quantify antibody titers, which were reported as mean luminescence signal (MLS), natural log corrected. P< 0.05 considered significant, corrected for multiple pairwise comparisons.

Results: We included 66 with COVID booster in pregnancy, 4 with booster postpartum, and 7 with COVID disease in pregnancy. COV2 RBD and Spike IgA and IgG were present in cordblood and persisted in infant serum through 30 days in those with COVID disease or booster in pregnancy (Fig 1). In breastmilk, COVID disease resulted in significantly higher systemic IgA and secretory IgA against both RBD and spike antigens compared to COVID booster (p=0.01, Fig 2). In contrast, infant serum Spike and RBD IgA and IgG were similar between those with COVID booster vs COVID disease in pregnancy. Infant titers were higher in those with COVID booster in pregnancy vs postpartum, although not statistically significant likely due to limited sample size (p=0.15 for IgA and 0.09 for IgG booster in pregnancy vs booster postpartum) (Fig 3). There was a strong correlation between breastmilk IgG (spike and RBD) and infant serum IgG at 30 days (p < 0.001), but not between breastmilk IgA (spike and RBD) and infant serum IgA in those with COVID booster in pregnancy (p>0.05).

Conclusion(s): COVID booster in pregnancy results in lasting vertical transfer of immunity through at least 30 days of life. Infant immunity is likely greater with COVID booster in pregnancy vs postpartum. Although there was greater secretory and systemic IgA in breastmilk following COVID disease vs booster, infant serum levels of IgA were similar. Further study is needed on the contribution of breastmilk vs maternal placental transfer to early infant immunity, and the potential to improve vaccination through improved secretory IgA generation.

Fig 1: Longevity of COVID related Antibody titers from delivery (cordblood) to 30 days or life.
In paired comparison between delivery and 30 days postpartum there was no significant decrease in titers (p>0.05). As expected, greater nucleocapsid (N) titers in those with COVID disease in pregnancy vs Booster vaccine.

Breastmilk IgA and IgG following maternal COVID booster vaccinaiton or COVID disease in pregnancy
Significantly higher secretory and systemic IgA in breastmilk of those with maternal COVID disease vs COVID booster vaccine in pregnancy (*p=0.01)

Infant Serum COVID related Antibody titers at 30 days of life
Similar serum spike IgA and IgG titers in infants of mothers exposed to COVID booster or COVID disease in pregnancy. Trend of higher levels of antibodies in infants of mothers who received COVID booster in pregnancy vs postpartum for IgA (p=0.15) and IgG (p=0.09)