The US Food and Drug Administration (FDA) is not in favor of antibody testing for SARS-CoV-2 testing to check immunity or protection from COVID-19, particularly among those who have been vaccinated.

As a reminder, the FDA advised against the use of antibody test results for these indications in a Safety Communication. Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDAs Center for Devices and Radiological Health said that antibody tests can be useful in identifying people who may have been exposed to the virus and may have developed an adaptive immune response. But the tests should not be used to as certain immunity or protection against COVID-19 at any time, particularly after having received a COVID-19 vaccination… (Medscape)