{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T15:31:28Z","timestamp":1771515088215,"version":"3.50.1"},"reference-count":31,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,11,10]],"date-time":"2025-11-10T00:00:00Z","timestamp":1762732800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathogens"],"abstract":"<jats:p>Standardized, one-size-fits-all COVID-19 booster schedules may be suboptimal due to individual variation in immune backgrounds, particularly prior infection, which induces robust hybrid immunity. This study estimated optimal booster timing by modeling antibody decay in relation to surrogate correlates of protection (CoP). In a prospective cohort of 177 Japanese healthcare workers, we longitudinally monitored anti-spike receptor-binding domain (S-RBD) antibody titers following BNT162b2 vaccination. Participants were stratified into SARS-CoV-2-na\u00efve and previously infected groups. Mixed-effects models were developed to predict when antibody titers would decline below predefined CoP thresholds. The model estimated optimal booster timing after a two-dose primary series to be 3\u20135 months for na\u00efve individuals and approximately one year for those with prior infection. Following a third dose, the estimated interval extended to 8\u201312 months for the na\u00efve group and 1.5\u20132 years for the previously infected group. These substantial differences underscore the limitations of uniform booster schedules. Our findings provide a quantitative framework for personalized vaccination strategies based on individual antibody profiles and immune status, thereby optimizing protection.<\/jats:p>","DOI":"10.3390\/pathogens14111138","type":"journal-article","created":{"date-parts":[[2025,11,10]],"date-time":"2025-11-10T13:51:08Z","timestamp":1762782668000},"page":"1138","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Estimating the Optimal COVID-19 Booster Timing Using Surrogate Correlates of Protection: A Longitudinal Antibody Study in Na\u00efve and Previously Infected Individuals"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5244-3992","authenticated-orcid":false,"given":"Yoshihiro","family":"Fujiya","sequence":"first","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ryo","family":"Kobayashi","sequence":"additional","affiliation":[{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Makito","family":"Tanaka","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ema","family":"Suzuki","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shiro","family":"Hinotsu","sequence":"additional","affiliation":[{"name":"Department of Biostatistics and Data Management, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mami","family":"Nakae","sequence":"additional","affiliation":[{"name":"Division of Infection Control, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9539-074X","authenticated-orcid":false,"given":"Yuki","family":"Sato","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuki","family":"Katayama","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6288-7696","authenticated-orcid":false,"given":"Masachika","family":"Saeki","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuki","family":"Yakuwa","sequence":"additional","affiliation":[{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shinya","family":"Nirasawa","sequence":"additional","affiliation":[{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Akemi","family":"Endoh","sequence":"additional","affiliation":[{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2743-3266","authenticated-orcid":false,"given":"Koji","family":"Kuronuma","sequence":"additional","affiliation":[{"name":"Division of Infection Control, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"},{"name":"Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Satoshi","family":"Takahashi","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Laboratory Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan"},{"name":"Division of Laboratory Medicine, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"},{"name":"Division of Infection Control, Sapporo Medical University Hospital, Sapporo 060-8543, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1412","DOI":"10.1056\/NEJMoa2101765","article-title":"BNT162b2 mRNA COVID-19 vaccine in a nationwide mass vaccination setting","volume":"384","author":"Dagan","year":"2021","journal-title":"N. 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