The CDC on Antibodies
Antibody tests check your blood by looking for antibodies, which can show if you had a past infection with the virus that causes COVID-19. Antibodies are proteins that help fight off infections and usually provide protection against getting that disease again (immunity). Antibodies are disease specific.
If you test positive or negative for COVID-19 on a viral or an antibody test, you still should take preventive measures to protect yourself and others.
We do not know yet if people who recover from COVID-19 can get infected again. Scientists are working to understand this.