Proficiency Sample 678 is an aliquot of human serum sample intended for use as a test sample in MSD’s V-PLEX COVID-19 Serology Kits. MSD provides assigned values for the concentration of antibodies to antigens from SARS-CoV-2, SARS-1, MERS, circulating Coronaviruses, and other respiratory disease viruses in each sample, enabling users to assess their laboratory performance for testing, training, concordance studies, validations, and troubleshooting. Proficiency Sample 678 is also available in MSD’s COVID-19 Proficiency Sample Panel 1, COVID-19 Proficiency Sample Panel 2, and COVID-19 Proficiency Sample Panel 3.