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Front Immunol
. 2025 Jul 28:16:1576016.
doi: 10.3389/fimmu.2025.1576016. eCollection 2025. Vaccination, infection, and hybrid immunity: determinants of SARS-CoV-2 IgG antibody levels and protection in Quzhou, China
Zhiying Yin # 1 , Mengcheng Yin # 2 , Fei Zhao # 3 , Canya Fu 3 , Wenjie Xu 1 , Quanjun Fang 1 , Xiaoying Gong 1 , Guoping Cao 1 , Canjie Zheng 1
Affiliations
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.
Keywords: COVID-19; SARS-CoV-2; hybrid immunity; infection; vaccination.
. 2025 Jul 28:16:1576016.
doi: 10.3389/fimmu.2025.1576016. eCollection 2025. Vaccination, infection, and hybrid immunity: determinants of SARS-CoV-2 IgG antibody levels and protection in Quzhou, China
Zhiying Yin # 1 , Mengcheng Yin # 2 , Fei Zhao # 3 , Canya Fu 3 , Wenjie Xu 1 , Quanjun Fang 1 , Xiaoying Gong 1 , Guoping Cao 1 , Canjie Zheng 1
Affiliations
- PMID: 40791592
- PMCID: PMC12336225
- DOI: 10.3389/fimmu.2025.1576016
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.
Keywords: COVID-19; SARS-CoV-2; hybrid immunity; infection; vaccination.