Quantitative antibody test

A method for quantitatively detecting a human antibody to BARS-CoV-2 S (spike) polypeptide, which method comprises:

• a) contacting a sample from a subject with a SARS-CoV-2 S (spike) polypeptide, or a fragment or analog thereof, to allow binding between an antibody to a SARS-CoV-2 S (spike) polypeptide, if present in said sample, and said SARS-CoV-2 S (spike) polypeptide, or a fragment or analog thereof;
• b) assessing a detectable signal due to binding between said antibody and said SARS-CoV-2 S (spike) polypeptide, or a fragment or analog thereof;
• and
• c) comparing said detectable signal to a calibration data set generated using a calibrator antibody that specifically binds to said SARS-CoV-2 S (spike) polypeptide at multiple concentrations or levels to assess amount, concentration or level of said antibody in said sample, and, optionally
• wherein said calibrator antibody is a chimeric antibody, or a fragment thereof, that comprises a human constant region and a variable region component or a variable region of a non-human species.