Quantitative Viral Serology
7-What do the results of my serology blood test mean?
Serology tests are often a valuable tool to identify previous infection and may help indicate
vaccine response, but sometimes these tests do not provide a definite answer.
Usually a negative test result means that no antibodies to COVID-19 antigens are found,
and it is likely that you have not had a COVID-19 infection, but there are some limitations. If
tested before two weeks from symptom onset, antibody results may be negative.
This means a negative test does not always rule out the cause of infection. Not everyone
who gets infected will develop antibodies to COVID-19. Antibody levels may decrease
over time. So, an antibody test performed early or late after symptom onset could be
negative. In regard to vaccine testing a negative result may indicate no or poor immune
A positive COVID-19 test result means you have IgG or IgM antibodies to the COVID-19
antigens tested, which may indicate that you have been infected by COVID-19 in the past,
but there are some limitations. In some instances, antibodies react with antigens that were
formed by another virus or substance. In these situations, the antibody is said to
cross-react with the tested antigens and will result in a positive lab test. It is unknown
whether having antibodies to SARS-CoV-2 will protect you from becoming infected again
or whether you can infect other people to SARS-CoV-2. You should continue to follow all
federal, state or local regulations to prevent the spread of COVID-19. The antibody test is
not used to diagnose a current COVID-19 infection. (If you have symptoms suggestive of
COVID-19 such as cough, shortness of breath, fever, or loss of taste or smell then please
contact your healthcare provider). Elevated IgG results when testing for vaccination
indicates an immune respose.
Sometimes a test result falls in between the negative and positive range. In such cases, it
may not be possible to tell whether a person has COVID-19 antibodies it is recommended
to redraw and test after 2 weeks.