Variant-Specific Kinetics of SARS-CoV-2 Anti-Nucleocapsid Antibodies and Household Transmission in Families During Anchestral, Alpha, Delta and Omicron Periods

TL;DR

This study shows how SARS-CoV-2 antibody levels change over time in children and adults and how different virus variants affect household transmission.

Contribution

The study reveals variant-specific antibody kinetics and the role of pediatric cases in household transmission during different SARS-CoV-2 waves.

Findings

Anti-nucleocapsid antibody levels peaked at three months and declined, with 89.2% remaining seropositive at 12 months.

Children had higher antibody levels than adults during Delta and Omicron periods, and pediatric cases increased household transmission risk.

Antibody waning was faster in secondary cases and during Omicron, but slower in those with higher initial antibody levels.

Abstract

To investigate SARS-CoV-2 antibody kinetics and household transmission, infected children along with their families were tested for anti-nucleocapsid antibodies at 1, 3, 6, 9 and 12 months post-SARS-CoV-2 infection during the Ancestral, Alpha, Delta, and Omicron waves. We prospectively included SARS-CoV-2 acute infected children (n = 189). After household recruitment (n = 76 households), the total study population was 228 children and 105 adults. The median age (IQR) of children and adults was 96 (115) months and 504 (96) months, respectively. Anti-nucleocapsid (anti-N) COI (cut-off index) titers peaked at three months post-infection and declined thereafter (p-value < 0.001), and 89.2% remained seropositive at 12 months. Children displayed significantly higher anti-N COI titers than adults during the Delta (p-value: 0.018) and Omicron (p-value: 0.047) periods. Household contact anti-N positivity (evidence of infection) was associated with pediatric index cases (aOR: 1.61, 95% CI: 1.11–2.35; p-value: 0.013) and elevated early anti-N COI titers (aOR: 1.24 per log10 unit, 95% CI: 1.05–1.48; p-value: 0.011). Higher secondary attacks were detected in Delta (aOR: 2.12, 95% CI: 1.19–3.77; p-value: 0.011) and Omicron (aOR: 2.75, 95% CI: 1.44–5.25; p-value: 0.002) compared to Ancestral. Waning of SARS-CoV-2 anti-N titers was faster in secondary cases (aHR: 1.62, 95% CI: 1.01–2.59; p-value: 0.047, Cox model) and during Omicron infection (aHR: 1.74 vs. Ancestral, 95% CI: 1.08–2.79; p-value: 0.023). In contrast, waning was slower in SARS-CoV-2 cases with higher baseline anti-N COI titers (aHR: 0.77, 95% CI: 0.64–0.93; p-value: 0.011). These findings demonstrate variant-specific, age-dependent antibody kinetics, emphasizing that pediatric index cases were associated with higher odds of household infection.

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