P-1600. Relationships between Anti-spike SARS-CoV-2 IgG Antibodies at Delivery, Timing of COVID-19 Vaccine Booster Doses in Pregnancy and Risk of Maternal and Infant Infections – The UK Preg-CoV Study

TL;DR

This study examines how timing of a COVID-19 vaccine booster during pregnancy affects antibody levels and infection risk in mothers and infants.

Contribution

The study provides new evidence on placental antibody transfer and the lack of correlation between antibody levels and postnatal infection risk.

Findings

Placental transfer of anti-S IgG antibodies is high across all trimesters.

No significant association was found between maternal antibody levels at delivery and postnatal infection rates in mothers or infants.

Trends suggest increased antibody responses when boosters are given later in pregnancy.

Abstract

The COVID-19 pandemic had a significant impact on pregnant women and infants, yet few prospective COVID-19 vaccine studies were undertaken. The Preg-CoV study examined the safety, immunogenicity and optimal timing of COVID-19 vaccine doses in a UK pregnancy cohort.Table 1.Maternal and cord/infant anti-spike SARS-CoV-2 IgG geometric mean concentrations (GMC), and placental transfer ratios (cord/infant blood:maternal blood ratio) by trimester of COVID-19 booster dose received during pregnancy.Figure 1.Kaplan-Meier curve for maternal infection post-delivery by anti-spike SARS-CoV-2 IgG antibody at delivery, below and above the median level (5605.4 ELU/ml).Includes participants receiving one COVID-19 dose during pregnancy as 3rd or 4th dose (booster). Excludes participants with anti-nucleocapsid evidence of infection without self-reported swab, participants with positive swab prior to delivery, participants with no anti-spike SARS-CoV-2 IgG at delivery. Participants are censored at the earliest date of withdrawal, loss to follow-up, end of study, or vaccination after delivery.

Maternal and cord/infant anti-spike SARS-CoV-2 IgG geometric mean concentrations (GMC), and placental transfer ratios (cord/infant blood:maternal blood ratio) by trimester of COVID-19 booster dose received during pregnancy.

Kaplan-Meier curve for maternal infection post-delivery by anti-spike SARS-CoV-2 IgG antibody at delivery, below and above the median level (5605.4 ELU/ml).

Includes participants receiving one COVID-19 dose during pregnancy as 3rd or 4th dose (booster). Excludes participants with anti-nucleocapsid evidence of infection without self-reported swab, participants with positive swab prior to delivery, participants with no anti-spike SARS-CoV-2 IgG at delivery. Participants are censored at the earliest date of withdrawal, loss to follow-up, end of study, or vaccination after delivery.

The Preg-CoV study is a Phase II, multi-centre, hybrid randomised and observational platform study of pregnant women and their infants. Participants from 13 sites were recruited Aug 2021 - Oct 2022. Maternal and cord/infant blood samples were taken at delivery or within 3 days of birth and anti-spike SARS-CoV-2 IgG geometric mean concentrations (anti-S IgG GMC, ELISA) and geometric mean placental transfer ratios (GMPTR) were measured. Episodes of SARS-CoV-2 infection (nasopharyngeal swabs, PCR/lateral flow) up to 12 months post-delivery were recorded.Figure 2.Kaplan-Meier curve for infant infection by maternal anti-spike SARS-CoV-2 IgG antibody at delivery, below and above the median level (6035.4 ELU/ml).Includes infants whose mothers received one COVID-19 dose during pregnancy as 3rd or 4th dose (booster). Excludes infants with no maternal anti-spike SARS-CoV-2 IgG at delivery. Infants censored at the earliest date of withdrawal, loss to follow-up, end of study.

Kaplan-Meier curve for infant infection by maternal anti-spike SARS-CoV-2 IgG antibody at delivery, below and above the median level (6035.4 ELU/ml).

Includes infants whose mothers received one COVID-19 dose during pregnancy as 3rd or 4th dose (booster). Excludes infants with no maternal anti-spike SARS-CoV-2 IgG at delivery. Infants censored at the earliest date of withdrawal, loss to follow-up, end of study.

317 (309 evaluable) participants were recruited. Median age at enrolment was 34 years (interquartile range [IQR] 30.4-36.7), median gestational age (GA) 28+4 weeks [23+0- 34+3], 54% had co-morbidities and 38% were SARS-CoV-2 seropositive; median GA at birth was 39+3 weeks [38+6- 40+4] and 36% delivered by caesarean section. 183 women received a 3rd or 4th COVID-19 vaccine booster dose during pregnancy whose GMPTR and cord/infant blood anti-S IgG levels at delivery were similar between trimester at receipt of their COVID-19 vaccine booster dose with an increased trend when the booster was given later in pregnancy (table 1). Of these participants, 32 (17%) had a positive swab antenatally and 26 (14%) postnatally. Of the 175 infants born to these women, 13 (7%) recorded a positive swab up to 12 months of age. Kaplan-Meier curves for postnatal infections (fig 1&2) demonstrate no significant association between maternal anti-S IgG antibody levels at delivery and COVID-19 infections. No COVID-19-related hospitalisations or deaths occurred.

Placental transfer of anti-S IgG antibodies is high ( > 1) across all trimesters, supporting a flexible maternal vaccination schedule, although trends suggest increased responses when a booster is given later in pregnancy. There was no evidence of a relationship between maternal anti-S IgG antibody level at delivery and subsequent mild infection rates in mothers or infants.

All Authors: No reported disclosures

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