The SARS-CoV-2 serology tests that eventually received FDA Emergency Use Authorization (EUA) have demonstrated high sensitivity and specificity, but that accuracy is for detecting antibodies. Their ability to predict protection against the virus based on those antibodies hasn't been proven. Plus, the FDA cautioned that some tests detect antibodies the immune system likely produces only after natural infection with the virus. Depending on the assay, people who weren't previously infected could test negative for antibodies despite having vaccine-induced immunity.

Therefore, the agency in its May 19 communication stated that "results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person's level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination."

The agency on Wednesday updated its list of tests impacted by virus mutations. While FDA continues to gather additional information and work with the three manufacturers to address these issues, it recommended the diagnostics not be used by clinical laboratory staff and healthcare providers.