High Frequency of Prior Severe Acute Respiratory Syndrome Coronavirus 2 Infection by Sensitive Nucleocapsid Assays

Prior infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is typically measured by nucleocapsid serology assays. In this study, we show that the Simoa serology assay and T-cell intracellular cytokine staining assay are more sensitive than the clinical Elecsys assay for detection of nucleocapsid-specific immune responses. These data suggest that the prevalence of prior SARS-CoV-2 infection in the population may be higher than currently appreciated.