Diagnostic manufacturers are turning their attention to antibodies for those who have been vaccinated for the SARS-CoV-2 virus, and the U.S. FDA’s Tim Stenzel had some advice about this on the Feb. 10 testing town hall. Stenzel advised that developers think of such tests in the same vein as a companion diagnostic (CDx) in that these antibody test will have to be separately validated for each vaccine that is included in the test’s labeled claims.