Internal Medicine
Online ISSN : 1349-7235
Print ISSN : 0918-2918
ISSN-L : 0918-2918
ORIGINAL ARTICLES
Factors Associated with Change in SARS-CoV-2 Antibody Titers from Three to Six Months after the Administration of the BNT162b2 mRNA COVID-19 Vaccine among Healthcare Workers in Japan: A Prospective Study
Takeshi MochizukiTakaki HoriKoichiro YanoKatsunori IkariKen Okazaki
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JOURNAL OPEN ACCESS

2022 Volume 61 Issue 8 Pages 1139-1143

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Abstract

Objective We evaluated the change in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody titers from three to six months after the administration of the BNT162b2 vaccine among healthcare workers.

Methods A total of 337 healthcare workers who received 2 doses of the BNT162b2 vaccine were included in this study. Factors associated with SARS-CoV-2 antibody titers at three and six months and the change in SARS-CoV-2 antibody titers between three and six months after vaccine administration were analyzed using a logistic regression analysis.

Results The SARS-CoV-2 antibody titer at 3 months was 4,812.1±3,762.9 AU/mL in all subjects and was lower in older workers than in younger ones. The SARS-CoV-2 antibody titer at 6 months was 1,368.9±1,412.3 AU/mL in all subjects. The SARS-CoV-2 antibody titers that were found to be high at three months were also high at six months. The change in SARS-CoV-2 antibody titers from 3 to 6 months was -68.9%±16.1%. The higher SARS-CoV-2 antibody titers at three months showed a more marked decrease from three to six months than lower titers.

Conclusion This study demonstrates that SARS-CoV-2 antibody titers at three months decreased with age and were associated with the antibody titers at six months and the change in titer from three to six months. Older individuals in particular need to be aware of the declining SARS-CoV-2 antibody titers at six months after the BNT162b2 vaccine. The results of this study may provide insight into COVID-19 vaccine booster strategies.

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© 2022 by The Japanese Society of Internal Medicine
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