Detection of SARS-CoV-2 nucleocapsid, spike, and neutralizing antibodies in vaccinated Japanese.

Abstract Serological detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N), spike (S), and neutralizing antibodies (Abs) is commonly undertaken to evaluate the efficacy of vaccination. However, the relative efficiency of different SARS-CoV-2 Ab detection systems has not been extensively investigated. Here, we evaluated serological test systems in vaccinated Japanese. SARS-CoV-2 N, S, and neutralizing Abs in sera of 375 healthy subjects a mean 253 days after vaccination were assessed. The sensitivity of Elecsys Anti-SARS-CoV-2 S (Roche S) and Anti-SARS-CoV-2 S IgG (Fujirebio S) was 100% and 98.9%, respectively, with a specificity of 100% for both. The sensitivity of Anti-SARS-CoV-2 neutralizing Ab (MBL Neu) was 2.7%, and the specificity was 100%. Fujirebio S correlated with Roche S (rho=0.9182, P=3.97X10-152). Fujirebio S (rho=0.1295, P=0.0121) and Roche S (rho=0.1232, P=0.0170) correlated weakly with MBL Neu. However, Roche S did correlate with MBL Neu in patients with COVID-19 (rho=0.8299, P=1.01X10-12) and in healthy subjects more recently after vaccination (mean of 90 days, rho=0.5306, P=0.0003). Thus, the Fujirebio S and Roche S results were very similar, but neither correlated with neutralizing antibody titers by MBL Neu at a later time after vaccination.