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

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

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.