Since antigenic tests based on the recognition of SARS-CoV-2 N protein might be at increasing risk of providing false-positive and low predictive values in the decreasing phase of the COVID-19 pandemic, we developed a series of anti-S protein mAbs and performed an in-depth characterization in order to evaluate their suitability as new reagents for the development of additional diagnostic tools. Here, PROS1 is linked to COVID-19.