{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T05:36:59Z","timestamp":1790314619612,"version":"4.1.0"},"reference-count":33,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T00:00:00Z","timestamp":1773360000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Life"],"abstract":"<jats:p>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 &lt; 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\u20132.35; p-value: 0.013) and elevated early anti-N COI titers (aOR: 1.24 per log10 unit, 95% CI: 1.05\u20131.48; p-value: 0.011). Higher secondary attacks were detected in Delta (aOR: 2.12, 95% CI: 1.19\u20133.77; p-value: 0.011) and Omicron (aOR: 2.75, 95% CI: 1.44\u20135.25; 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\u20132.59; p-value: 0.047, Cox model) and during Omicron infection (aHR: 1.74 vs. Ancestral, 95% CI: 1.08\u20132.79; 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\u20130.93; 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.<\/jats:p>","DOI":"10.3390\/life16030470","type":"journal-article","created":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T11:12:25Z","timestamp":1773400345000},"page":"470","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Variant-Specific Kinetics of SARS-CoV-2 Anti-Nucleocapsid Antibodies and Household Transmission in Families During Anchestral, Alpha, Delta and Omicron Periods"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2775-3670","authenticated-orcid":false,"given":"Filippos","family":"Filippatos","sequence":"first","affiliation":[{"name":"Infectious Diseases and Chemotherapy Research Laboratory, First Department of Pediatrics, Medical School, National and Kapodistrian University of Athens, \u201cAghia Sophia\u201d Children\u2019s Hospital, 11527 Athens, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7325-6195","authenticated-orcid":false,"given":"Elizabeth-Barbara","family":"Tatsi","sequence":"additional","affiliation":[{"name":"Infectious Diseases and Chemotherapy Research Laboratory, First Department of Pediatrics, Medical School, National and Kapodistrian University of Athens, \u201cAghia Sophia\u201d Children\u2019s Hospital, 11527 Athens, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0592-9591","authenticated-orcid":false,"given":"Vassiliki","family":"Syriopoulou","sequence":"additional","affiliation":[{"name":"Infectious Diseases and Chemotherapy Research Laboratory, First Department of Pediatrics, Medical School, National and Kapodistrian University of Athens, \u201cAghia Sophia\u201d Children\u2019s Hospital, 11527 Athens, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1745-1118","authenticated-orcid":false,"given":"Athanasios","family":"Michos","sequence":"additional","affiliation":[{"name":"Infectious Diseases and Chemotherapy Research Laboratory, First Department of Pediatrics, Medical School, National and Kapodistrian University of Athens, \u201cAghia Sophia\u201d Children\u2019s Hospital, 11527 Athens, Greece"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"902","DOI":"10.1038\/s41590-021-01089-8","article-title":"Children develop robust and sustained cross-variant humoral immunity after SARS-CoV-2 infection","volume":"23","author":"Dowell","year":"2022","journal-title":"Nat. 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