COVID Antibodies

While it is not a good test for active infection, antibody testing is useful in assessing for prior infections, asymptomatic cases, and possible immunity/protection from reinfection. While there is still much about COVID-19 we do not yet understand, the general agreement is that the presence of antibodies indicates prior infection with COVID-19 or prior immunization and serves as some degree of protection from re-infection. Re-infection with COVID-19 is rare, and most cases of re-infection are mild, which would indicate there is some protection after recovering from COVID-19.

IgM is usually the first antibody the body produces in response to infection, but typically IgM levels will wane quickly after the initial infection. IgG antibodies serve as long term protection against future infection. In the case of COVID-19 most patients develop IgM and IgG antibodies within a few days of each other. The presence of both IgM and IgG would indicate a more recent infection, whereas the presence only of IgG would indicate a more remote infection.

No- if you are not having symptoms. A positive antibody test would indicate prior infection and would not require any changes to your current activities. If anything it would indicate some degree of immunity from re-infection.

If you are having symptoms, or a known direct exposure, current isolation and quarantine restrictions still apply regardless of antibody test results. For patients with symptoms the appropriate test would be a COVID-Antigen or PCR test.

While antibodies offer protection against re-infections and subsequent spread to those around us, there is still much we do not understand about COVID-19. Not all infections result in life-long immunity. Some patients can lose their antibodies months after their initial infection. The presence of antibodies does not guarantee immunity against re-infection.

 COVID-19 vaccination results in an antibody response specifically against the surface spike protein. The test we are using does detect antibodies directed at the surface spike protein and other COVID-19 antibodies, so in theory antibodies from the vaccine could show up on our test. Unfortunately that specific scenario has not been formally tested by the manufacturer and so we cannot say for certain the vaccine generated antibodies react with our test.