Antibodies are proteins created by your immune system that help you fight off infections. They are made after you have been infected or have been vaccinated against an infection.
If your body develops an immune response to vaccination, which is the goal, you may test positive on some antibody tests. Antibody tests indicate you had a previous infection and that you may have some level of protection against the virus. Learn more about the possibility of COVID-19 illness after vaccination.
Both SARS-CoV-2 IgM and IgG antibodies may be detected around the same time after infection. However, while IgM is most useful for determining recent infection, it usually becomes undetectable weeks to months following infection; in contrast, IgG is usually detectable for longer periods.
IgG antibodies to SARS-CoV-2 are generally detectable in blood several days after initial infection, although the duration of time antibodies are present post-infection is not well characterized. Individuals may have detectable virus present for several weeks following seroconversion.
An antibody test cannot be used to diagnose current COVID-19 because an antibody test does not detect SARS-CoV-2. Only COVID-19 diagnostic tests can be used to diagnose current COVID-19. A positive antibody test result can be used to help identify people who may have had a prior SARS-CoV-2 infection or prior COVID-19.
Antibody tests, also called serology tests, measure antibodies to coronavirus in the blood. If you have antibodies, it means you've been exposed to the virus and your immune system has made antibodies against it. Antibody tests are different from the tests doctors use to check for the virus itself.
The Tell Me Fast Novel Coronavirus (COVID- 19) IgG/IgM Antibody Test is intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating recent or prior infection.
The Assure COVID-19 IgG/IgM Rapid Test Device should not be used to diagnose acute SARS-CoV-2 infection.
Reverse transcription polymerase chain reaction (RT-PCR)-based diagnostic tests (which detect viral nucleic acids) are considered the gold standard for detecting current SARS-CoV-2 infection.
A negative test means that you have no COVID-19 antibodies, so you probably were not infected with the COVID-19 virus in the past. Because it takes time for antibodies to develop, false-negative test results can happen if the blood sample is collected too soon after your infection started.
Although the immune correlates of protection are not fully understood, evidence indicates that antibody development following infection likely confers some degree of immunity from subsequent infection for at least 6 months.
It is important to remember that some people with antibodies to SARS-CoV-2 may become infected after vaccination (vaccine breakthrough infection) or after recovering from a past infection (reinfected).