Abstract
Current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological tests are based on the full-length spike (S), the receptor-binding domain (RBD), or the nucleoprotein (NP) as substrates. Here, we used samples from healthcare workers (HCWs) to perform a longitudinal analysis of the antibody responses using a research-grade RBD and spike-based enzyme-linked immunosorbent assay (ELISA), a commercial RBD and spike-based ELISA, and a commercial NP-based chemiluminescent microparticle immunoassay. Seroprevalence ranged around 28% early during the pandemic and a good correlation was observed between RBD and spike-based ELISAs. Modest correlations were observed between NP and both RBD and spike-based assays. The antibody levels in HCWs declined over time; however, the overall seroprevalence measured by RBD and spike-based assays remained unchanged, while the seroprevalence of NP-reactive antibodies significantly declined. Moreover, RBD and spike-based assays effectively detected seroconversion in vaccinees. Overall, our results consolidate the strength of different serological assays to assess the magnitude and duration of antibodies to SARS-CoV-2.