The FDA issued information on the use of serological (antibody) tests to help identify COVID-19 infections.
In a letter to healthcare providers, the FDA states that such tests should not be used as the sole basis for diagnosis of COVID-19, stating that the agency is not aware of any antibody tests that are validated for diagnosis of infection. Antibodies may not be present in detectable levels during the early states of COVID-19 infection, and such tests could lead to false negative test results. In some cases, infected patients may not even develop antibodies at all.
In another communication, the FDA clarified that antibody tests have the potential to identify who was infected and is currently carrying antibodies; such tests are important in determining who can donate convalescent plasma. As plasma rich in antibodies can benefit those currently suffering from COVID-19, the FDA is working to expand access to these tests.
However, it must be noted that having antibodies does not guarantee full protection from reinfection, and there is no certainty on how long immunity lasts.