{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:21:40Z","timestamp":1785410500504,"version":"3.56.0"},"reference-count":34,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T00:00:00Z","timestamp":1781049600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003399","name":"Science and Technology Commission of Shanghai Municipality","doi-asserted-by":"publisher","award":["25DX2800200"],"award-info":[{"award-number":["25DX2800200"]}],"id":[{"id":"10.13039\/501100003399","id-type":"DOI","asserted-by":"publisher"}]},{"award":["25DX2800200"],"award-info":[{"award-number":["25DX2800200"]}],"id":[{"id":"https:\/\/ror.org\/03kt66j61","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Shanghai Municipal Science and Technology Major Project","award":["ZD2021CY001"],"award-info":[{"award-number":["ZD2021CY001"]}]},{"DOI":"10.13039\/100017950","name":"Shanghai Municipal Health Commission","doi-asserted-by":"publisher","award":["202240081"],"award-info":[{"award-number":["202240081"]}],"id":[{"id":"10.13039\/100017950","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: SARS-CoV-2 reinfections increased substantially after the emergence of Omicron variants. Methods: We conducted a cross-sectional study of 2095 individuals with prior Omicron BA.2 infection in Shanghai, China, during the early post-zero-COVID period. Data on demographics, infection history, and lifestyle factors were collected via questionnaire, and blood samples were obtained for ancestral RBD-blocking antibody measurement. Results: Meeting WHO physical activity recommendations (\u2265600 MET-min\/week) was associated with lower reinfection odds (OR = 0.59, 95% CI: 0.46\u20130.74, p &lt; 0.001). The overall median ancestral RBD-blocking antibody level was 263.93 U\/mL (IQR: 36.41\u2013331.87). Older age was associated with lower ancestral RBD-blocking antibody levels (\u03b2 = \u20130.0038 per year, 95% bootstrap CI: \u20130.0057 to \u20130.0019, p &lt; 0.001). All vaccinated groups had significantly higher ancestral RBD-blocking antibody levels than unvaccinated individuals: partially vaccinated (\u03b2 = 0.4440, 95% CI: 0.1569 to 0.6830, p &lt; 0.001), fully vaccinated (\u03b2 = 0.8516, 95% CI: 0.7464 to 0.9595, p &lt; 0.001), homologous booster (\u03b2 = 1.0297, 95% CI: 0.9408 to 1.1223, p &lt; 0.001), and heterologous booster (\u03b2 = 1.0838, 95% CI: 0.9387 to 1.2226, p &lt; 0.001). Time since last immune event was inversely associated with ancestral RBD-blocking antibody levels (\u03b2 = \u20130.0232 per month, 95% CI: \u20130.0385 to \u20130.0077, p = 0.0031). Conclusions: In this cross-sectional study, meeting WHO physical activity recommendations was associated with 41% lower odds of SARS-CoV-2 reinfection, although reverse causality cannot be ruled out. All vaccinated groups had higher ancestral RBD-blocking antibody levels than unvaccinated individuals. Older age and longer time since last immune event were associated with lower ancestral RBD-blocking antibody levels. These associations need confirmation in prospective, well-powered studies.<\/jats:p>","DOI":"10.3390\/vaccines14060520","type":"journal-article","created":{"date-parts":[[2026,6,11]],"date-time":"2026-06-11T02:59:31Z","timestamp":1781146771000},"page":"520","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Characteristics of SARS-CoV-2 Reinfection and Ancestral RBD-Blocking Antibody Levels: A Cross-Sectional Study in the Post-Zero-COVID Era from Shanghai"],"prefix":"10.3390","volume":"14","author":[{"given":"Chen","family":"Chen","sequence":"first","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuanfei","family":"Zhu","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"},{"name":"Key Laboratory of Medical Molecular Virology (MOE\/NHC\/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Huiting","family":"Wang","sequence":"additional","affiliation":[{"name":"Minhang District Center for Disease Control and Prevention, Shanghai 201101, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fei","family":"Wu","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Youhua","family":"Xie","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"},{"name":"Key Laboratory of Medical Molecular Virology (MOE\/NHC\/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qingqing","family":"Jia","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Yang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Medical Molecular Virology (MOE\/NHC\/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiangjiang","family":"Lyu","sequence":"additional","affiliation":[{"name":"Xietu Street Community Health Service Center, Xuhui District, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Junqiang","family":"Qu","sequence":"additional","affiliation":[{"name":"Longhua Street Community Health Service Center, Xuhui District, Shanghai 200232, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6416-1733","authenticated-orcid":false,"given":"Qiao","family":"Wang","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"},{"name":"Key Laboratory of Medical Molecular Virology (MOE\/NHC\/CAMS), Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China"},{"name":"Shanghai Fifth People\u2019s Hospital, Fudan University, Shanghai 200240, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fan","family":"Wu","sequence":"additional","affiliation":[{"name":"Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China"},{"name":"Shanghai Medical College, Fudan University, Shanghai 200032, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e2381","DOI":"10.1002\/rmv.2381","article-title":"Evolution of the SARS-CoV-2 omicron variants BA.1 to BA.5: Implications for immune escape and transmission","volume":"32","author":"Shrestha","year":"2022","journal-title":"Rev. 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