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Publications

Journal Article Epublish

PubMed: 40791592 DOI: 10.3389/fimmu.2025.1576016

Vaccination, infection, and hybrid immunity: determinants of SARS-CoV-2 IgG antibody levels and protection in Quzhou, China.

Front Immunol 16:1576016

Authors: Zhiying Yin, Mengcheng Yin, Fei Zhao, Canya Fu, Wenjie Xu, Quanjun Fang, Xiaoying Gong, Guoping Cao, Canjie Zheng

Affiliations

  • Department of Immunity, Quzhou Center for Disease Control and Prevention, Quzhou, Zhejiang, China.
  • Second Clinical Medical College, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
  • Department of Epidemiology, School of Public Health, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China.

Abstract

Objectives

To investigate the factors influencing SARS-CoV-2 IgG antibody levels and protection in a population that has experienced both vaccination and COVID-19 infections, predominantly caused by the Omicron BA.5.2 and BF.7 variants.

Methods

Anti-SARS-CoV-2 IgG antibody levels were measured using chemiluminescent microparticle immunoassay (CMIA). Multivariate regression analyses assessed factors influencing antibody levels, and decision tree models predicted variable priorities.

Results

Among the 3494 participants, the median (IQR) anti-SARS-CoV-2 IgG level was 396.53 (280.51-471.03) AU/mL, with a seropositive rate of 97.28%. Multivariate analysis revealed that vaccination status, infection status, residence county, occupation, and vaccination interval were significantly associated with antibody concentration. The decision tree model indicated that vaccination had a greater effect on antibody concentration than infection, while infection had a stronger impact on seropositivity. The Breakthrough Infection group had the highest antibody concentration compared with other groups.

Conclusions

Vaccination and infection were identified as the primary determinants of SARS-CoV-2 IgG antibody levels, with hybrid immunity significantly enhancing antibody responses. New evaluation methods or revised detection thresholds were needed to better assess population immunity.

MeSH

Sars-Cov-2, Vaccines, Vaccination, Immunity, Severe Acute Respiratory Syndrome-Related Coronavirus, Immunoglobulin G, Infections