Kinetics of anti-SARS-CoV-2 antibody titer in healthy adults up to 6 months after BNT162b2 vaccination measured by two immunoassays: A prospective cohort study in Japan |
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| Affiliation: | 1. Department of Public Health, Graduate School of Medicine, Osaka Metropolitan University, Osaka, Japan;2. Research Center for Infectious Disease Sciences, Graduate School of Medicine, Osaka Metropolitan University, Japan;3. Department of Virology and Parasitology, Graduate School of Medicine, Osaka Metropolitan University, Japan;4. Management Bureau, Osaka Metropolitan University Hospital, Japan;5. Department of Orthopedic Surgery, Graduate School of Medicine, Osaka Metropolitan University, Japan;6. Department of Medical Quality and Safety Science, Graduate School of Medicine, Osaka Metropolitan University, Japan;7. Department of Bacteriology, Graduate School of Medicine, Osaka Metropolitan University, Japan;8. Department of Infection Control Science, Graduate School of Medicine, Osaka Metropolitan University, Japan;9. Clinical Epidemiology Research Center, SOUSEIKAI Medical Group (Medical Co. LTA), Fukuoka, Japan |
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| Abstract: | BackgroundAlthough several assays are used to measure anti-receptor-binding domain (RBD) antibodies induced after severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccination, the assays are not fully comparable in practice. This study evaluated the immunogenicity of the BNT162b2 mRNA vaccine in healthy adults using two immunoassays.MethodsThis prospective cohort study included SARS-CoV-2-naïve adults, predominantly healthcare workers, aged 20–64 years, who received two BNT162b2 vaccine doses between March and May 2021. Blood samples were collected before the first vaccination (S0), before the second vaccination (S1), 4 weeks after the second vaccination (S2), and 6 months after the second vaccination (S3). anti-RBD antibodies were measured using the Architect SARS-CoV-2 IgG II Quant (Abbott Laboratory) and Elecsys anti-SARS-CoV-2 S (Roche Diagnostics) assays.ResultsAmong the 385 participants, the geometric mean antibody titers (GMTs) on the Architect assay (AU/mL) were 7.5, 693, 7007, and 1030 for S0, S1, S2, and S3, respectively. The corresponding GMTs on the Elecsys assay (U/mL) were 0.40, 24, 928, and 659, respectively. The GMT ratio (S3/S2) was 0.15 on the Architect and 0.71 on the Elecsys assay. The correlation between antibody titers measured with the two assays were strong at all time points after vaccination (Spearman's correlation coefficient: 0.74 to 0.86, P < 0.01 for all). GMT was significantly lower in the older age group after vaccination (P < 0.01), with no significant differences according to sex. Seroprotection (≥5458 AU/mL on the Architect assay and ≥ 753 U/mL on the Elecsys) at each time point was 0 %, 1 %, 67 %, and 1 % on the Architect assay and 0 %, 1 %, 62 %, and 43 % on the Elecsys, respectively.ConclusionsTwo BNT162b2 vaccine doses resulted in adequate anti-RBD antibody response, which varied by age. As the two assays showed different kinetics, the results of single immunoassays should be interpreted with caution. |
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| Keywords: | SARS-CoV-2 Vaccination Immunoassay mRNA vaccine Japan BNT162b2 anti-RBD antibody response Architect SARS-CoV-2 IgG II Quant Elecsys Anti-SARS-CoV-2 S |
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