{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,7]],"date-time":"2025-11-07T05:15:44Z","timestamp":1762492544198,"version":"build-2065373602"},"reference-count":41,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,10,29]],"date-time":"2025-10-29T00:00:00Z","timestamp":1761696000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Background\/Objectives: The anti-spike (S) SARS-CoV-2 antibodies confer neutralizing properties and their concentration may be related to COVID-19 protection. Anti-nucleocapsid (N) SARS-CoV-2 antibodies in mRNA COVID-19 vaccine recipients indicate infection. The aim of this study was to analyze the anti-S and anti-N titers 3 years after COVID-19 vaccination. Methods: Ninety-nine vaccinated healthcare workers provided blood samples in 2024 and filled out questionnaires about their COVID-19 history and boosters acceptance. Anti-spike and anti-nucleocapsid IgG were assessed with commercially available immunoassays, DiaSorin\u2019s SARS-CoV-2 TrimericS IgG and Abbott\u2019s SARS-CoV-2 IgG, respectively. Results: Three years after the primary COVID-19 vaccination, the anti-S SARS-CoV-2 antibody concentration was still high. However, it dropped in comparison to the data obtained a year before (3600 vs. 2040 BAU\/mL), possibly due to the lack of boosters. In contrast, the percentage of anti-N seropositive individuals grew from 34% two years after vaccination to 40.4% after three years. Subjects with SARS-CoV-2 infection within a year prior to the antibody measurements had statistically significantly higher median anti-S concentrations than those with tentatively no contact with SARS-CoV-2 (2940 vs. 1930 BAU\/mL). Conclusions: Overall, our data indicates that although the booster vaccinations\u2019 acceptance decreases, the circulating SARS-CoV-2 stimulates humoral immunity, resulting in high anti-S antibody concentrations even three years after the vaccination.<\/jats:p>","DOI":"10.3390\/v17111443","type":"journal-article","created":{"date-parts":[[2025,10,29]],"date-time":"2025-10-29T17:38:22Z","timestamp":1761759502000},"page":"1443","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Three Years After COVID-19 Vaccination, Anti-Spike SARS-CoV-2 Antibody Concentration Decreases and Is Accompanied by Increasing Anti-Nucleocapsid Seropositivity"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3416-5658","authenticated-orcid":false,"given":"Tomasz","family":"Anyszek","sequence":"first","affiliation":[{"name":"Medical Faculty, Andrzej Frycz Modrzewski Krakow University, 30-705 Krakow, Poland"},{"name":"Medical Department Diagnostyka S.A., 31-864 Krakow, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8757-360X","authenticated-orcid":false,"given":"Jakub","family":"Swad\u017aba","sequence":"additional","affiliation":[{"name":"Medical Faculty, Andrzej Frycz Modrzewski Krakow University, 30-705 Krakow, Poland"},{"name":"Medical Department Diagnostyka S.A., 31-864 Krakow, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andrzej","family":"Panek","sequence":"additional","affiliation":[{"name":"Medical Department Diagnostyka S.A., 31-864 Krakow, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9847-9811","authenticated-orcid":false,"given":"Emilia","family":"Martin","sequence":"additional","affiliation":[{"name":"Medical Department Diagnostyka S.A., 31-864 Krakow, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,29]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2025, January 29). 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