{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T16:37:20Z","timestamp":1783528640729,"version":"3.55.0"},"reference-count":34,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2022,1,20]],"date-time":"2022-01-20T00:00:00Z","timestamp":1642636800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Research on post-vaccination antibody dynamics has become pivotal in estimating COVID-19 vaccine efficacy. We studied anti-SARS-CoV-2 Spike RBD IgG levels in 587 healthcare workers (2038 sera) who completed BNT162b2 vaccination. Average antibody titer 3 weeks after the first dose in COVID-19-na\u00efve participants (median 873.5 AU\/mL) was 18-fold higher than the test threshold, with a significant increase 1 month (median 9927.2 AU\/mL) and an exponential decrease 3 (median 2976.7 AU\/mL) and 6 (median 966.0 AU\/mL) months after complete vaccination. Participants with a history of COVID-19 prior to vaccination showed significantly higher antibody levels, particularly after the first dose (median 14,280.2 AU\/mL), with a slight decline 1 month (median 12,700.0 AU\/mL) and an exponential decline in antibody titers 3 (median 4831.0 AU\/mL) and 6 (median 1465.2 AU\/mL) months after vaccination. Antibody levels of COVID-19-na\u00efve subjects after the first dose were moderately correlated with age (r = \u22120.4). Multivariate analysis showed a strong independent correlation between IgG levels 6 months after vaccination and both IgG titers after the first dose and 1 month after vaccination (R2 = 0.709). Regardless of pre-vaccination COVID-19 history, IgG levels 6 months after vaccination were comparable to antibody levels reached by COVID-19-na\u00efve participants after the first vaccine dose.<\/jats:p>","DOI":"10.3390\/vaccines10020153","type":"journal-article","created":{"date-parts":[[2022,1,20]],"date-time":"2022-01-20T22:59:57Z","timestamp":1642719597000},"page":"153","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":34,"title":["Decline of Anti-SARS-CoV-2 IgG Antibody Levels 6 Months after Complete BNT162b2 Vaccination in Healthcare Workers to Levels Observed Following the First Vaccine Dose"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8023-4314","authenticated-orcid":false,"given":"Oktavija","family":"\u0110akovi\u0107 Rode","sequence":"first","affiliation":[{"name":"Department for Clinical Microbiology, Division for Virology, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"},{"name":"School of Dental Medicine, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1212-3302","authenticated-orcid":false,"given":"Kristian","family":"Boduli\u0107","sequence":"additional","affiliation":[{"name":"Research Department, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sanja","family":"Zember","sequence":"additional","affiliation":[{"name":"Health Care Quality Unit, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nata\u0161a","family":"Cetini\u0107 Balent","sequence":"additional","affiliation":[{"name":"Department for Clinical Microbiology, Division for Virology, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"An\u0111a","family":"Novokmet","sequence":"additional","affiliation":[{"name":"Department for Adult Intensive Care and Neuroinfections, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marija","family":"\u010culo","sequence":"additional","affiliation":[{"name":"Department for Clinical Microbiology, Division for Bacteriology, Hospital Infections and Sterilization, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u017deljka","family":"Ra\u0161i\u0107","sequence":"additional","affiliation":[{"name":"Health Care Quality Unit, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Radojka","family":"Mikuli\u0107","sequence":"additional","affiliation":[{"name":"Department for Clinical Microbiology, Division for Virology, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alemka","family":"Markoti\u0107","sequence":"additional","affiliation":[{"name":"Research Department, University Hospital for Infectious Diseases \u201cDr. Fran Mihaljevi\u0107\u201d, 10000 Zagreb, Croatia"},{"name":"School of Medicine, Catholic University of Croatia, 10000 Zagreb, Croatia"},{"name":"Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"596201","DOI":"10.3389\/fcimb.2021.596201","article-title":"Wuhan to World: The COVID-19 Pandemic","volume":"11","author":"Kumar","year":"2021","journal-title":"Front. 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