Neutralizing-antibody response to SARS-CoV-2 for 12 months after the COVID-19 workplace outbreaks in Japan

Azumi Ishizaki, Xiuqiong Bi, Quynh Thi Nguyen, Tomomi Maeno, Akinori Hara, Hiroyuki Nakamura, Sanae Kuramoto, Koichi Nishi, Hiroyasu Ooe, Hiroshi Ichimura

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


This study aimed to elucidate the 12-month durability of neutralizing antibodies (NAbs) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients infected during the 2020 workplace outbreaks of coronavirus disease 2019 (COVID-19) in Japan. We followed 33 Japanese patients infected with SARS-CoV-2 in April 2020 for 12 months (12M). Patients were tested for NAbs and for antibodies against the SARS-CoV-2 nucleocapsid (anti-NC-Ab) and antibodies against the spike receptor-binding domain (anti-RBD-Ab). Tests were performed at 2M, 6M, and 12M after the primary infection (api) with commercially available test kits. In 90.9% (30/33) of patients, NAbs persisted for 12M api, though the median titers significantly declined from 78.7% (interquartile range [IQR]: 73.0-85.0%) at 2M, to 59.8% (IQR: 51.2-77.9) at 6M (P = 0.008), and to 56.2% (IQR: 39.6-74.4) at 12M (P<0.001). An exponential decay model showed that the NAb level reached undetectable concentrations at 35.5 months api (95% confidence interval: 26.5-48.0 months). Additionally, NAb titers were significantly related to anti-RBD-Ab titers (rho = 0.736, P<0.001), but not to anti-NC-Ab titers. In most patients convalescing from COVID-19, NAbs persisted for 12M api. This result suggested that patients need a booster vaccination within one year api, even though NAbs could be detected for over two years api. Anti-RBD-Ab titers could be used as a surrogate marker for predicting residual NAb levels.

Original languageEnglish (US)
Pages (from-to)e0273712
JournalPloS one
Issue number8
StatePublished - 2022
Externally publishedYes


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Antibody Formation
  • COVID-19/epidemiology
  • Disease Outbreaks
  • Humans
  • Japan/epidemiology
  • SARS-CoV-2
  • Spike Glycoprotein, Coronavirus
  • Workplace


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