ABSTRACT
Background. Natural SARS-CoV-2 infection results in anti-nucleocapsid (N) and anti-spike (S) antibody (Ab) development. Anti-S Ab response (conferred by infection and/or vaccination) is more closely associated with protection. We evaluated anti-N/S Ab responses in vaccinated (> 1 dose) and unvaccinated pregnant people with prior SAR-CoV-2 infection. Methods. During January 2021-March 2022, we enrolled participants with SARS-CoV-2 infection identified in pregnancy (26 via anti-N IgG+;52 via prior RT-PCR+). Baseline, 1, 2, 3, 6, and 12 months, and delivery samples were tested for anti-N (index >= 1.4 positive) and anti-S (>= 50 AU/mL positive) IgG Ab by Abbott Architect. Kaplan-Meier methods were used to measure Ab response duration. Results. Among 78 participants, 62 (79%) enrolled in pregnancy (median 27 weeks gestation), and 16 (21%) at delivery/postpartum (median 2 weeks);34 (44%) had received >=1 vaccine prior to initial Ab testing. At baseline, 59 (75%) participants had concordant anti-N/S positive results (median anti-N index 3.58 [IQR 2.01-5.82], median anti-S 5529 AU/ml [IQR 687-25000]). Anti-S IgG was higher (25000 vs 774, p< 0.001) among participants receiving >=1 vaccine vs no vaccine, while anti-N IgG indices were similar. Among 59 participants with initial anti-N IgG+ results, median time to anti-N IgG negative results was 31 weeks after first RT-PCR+ (median 17 weeks after first anti-N IgG+ result). Only 1 (unvaccinated) participant had an anti-S IgG negative result by 22 weeks after first RT-PCR+ result. Among 30 participants with delivery samples (median 16 weeks after RT-PCR+, 12 weeks after baseline anti-N IgG+ samples), 15 (52%) remained anti-N IgG+;29 (97%) remained anti-S IgG+. Anti-S IgG was higher (25000 vs 826 AU/ml, p< 0.001) among participants receiving >= 1 vaccine vs. no vaccine prior to delivery. Conclusion. Among pregnant persons with prior SARS-CoV-2 infection, duration of anti-S IgG response was longer than anti-N IgG irrespective of vaccine status;vaccination during pregnancy was associated with higher anti-S levels at baseline and delivery. While anti-S IgG were detectable for >= 6 months, longer term follow-up is needed to assess durability of hybrid immunity vs. infection alone and has implications for maternal and infant protection.
ABSTRACT
Background. Antenatal care is a unique opportunity to assess SARS-CoV-2 seroprevalence and antibody response in pregnant people, including those with previously unknown infection. Methods. Pregnant people were screened for SARS-CoV-2 IgG during antenatal care or delivery in Seattle, Washington with Abbott Architect chemiluminescent immunoassay which provides quantitative index (positive ≥1.4). Participants with IgG+ results or identified with RT-PCR+ results via medical records were invited to enroll in a longitudinal evaluation of antibody responses. We report preliminary results of an ongoing seroprevalence and longitudinal study with planned 18-month follow-up. Results. Between September 9, 2020-May 7, 2021, we screened 1304 pregnant people;62 (4.8%) tested SARS-CoV-2 IgG+, including 28 (45%) with known prior SARS-CoV-2 infection. Among participants testing IgG+, median age was 32 years (interquartile range [IQR] 26-35) and median gestational age was 21 weeks (IQR 12-38) at screening;median IgG index was 3.2 (IQR 2.1-4.9, range 1.4-9.9), including 3.9 (IQR 2.3-5.8) among those with vs. 2.7 (IQR 1.9-4.2) among those without prior RT-PCR+ results (p=0.05 by Wilcoxon rank-sum). Of 30 longitudinal study participants enrolled, 24 tested IgG+ at baseline (75% with prior RT-PCR+ result) and 6 tested IgG- on enrollment but were identified as previously RT-PCR+ via medical records;24/30 (80%) reported previous symptoms. Of 24 participants testing IgG+ at baseline, 14 (58%) had first follow-up IgG results at median of 66 days (IQR 42-104) since initial testing, with median IgG index of 2.0 (IQR 1.0-3.8). 9/14 (64%) participants with repeat IgG testing remained IgG+ at first follow-up (≤280 days after first RT-PCR+ result for those with and ≥104 days after first IgG detection for those without prior RT-PCR+ results), while 5/14 (26%) had a negative Abbott IgG test at a median of 81 days (IQR 75-112) since initial testing. Conclusion. Nearly half of pregnant people testing SARS-CoV-2 IgG+ reported no known prior SARS-CoV-2 diagnosis or symptoms. SARS-CoV-2 IgG antibody response and durability in pregnancy has implications for maternal and neonatal protection and susceptibility and highlights potential benefits of vaccination in this population.