Antibody tests cannot be used alone to rule out COVID-19. However, they can serve an important role. Using antibody tests on many patients may help the medical community better understand the immune response in patients over time and how many people may have been infected. In the future, it is also possible that they may also be used to help determine, together with other clinical data, that some individuals are no longer susceptible to infection. In addition, these test results can aid in determining who may donate a part of their blood called convalescent plasma, which may serve as a possible treatment for those who are seriously ill from COVID-19.