Unlike the antigen test, the antibody test looks for the antibodies created by the B-cells in the body to fight the antigens. It is detected through the blood of people who have been previously infected with the coronavirus. However, it is also possible to detect antibodies from vaccines, meaning the test isn't as reliable to diagnose the current infection (Centers for Disease . The first blood antibody test for HIV was approved by the FDA in March of 1985 (Smithsonian National Museum of American History, n.d.). However, since then, a lot about the test has changed, such as testing saliva instead of blood and quicker test results.