PROS1 and COVID-19: The tendency of a subset of these peptides to detect remarkably low quantities of the S protein in cell lysate mixtures (as low as 100 pg/ml), in addition to the speed (<2 weeks versus months for the monoclonal antibody-based counterpart) and the low cost (negligible vs. thousands of dollars) of our peptide design and development, collectively render our approach attractive for the streamlined development of COVID-19 peptide diagnostics.