The Public Health Agency of Sweden
Updated 15 November 2021

An antibody test can show if you have already had COVID-19

An antibody test can show if you have already had COVID-19 or been vaccinated and developed antibodies against the virus.

To test if you have had COVID-19, an antibody test, is performed by taking a blood sample. It may take time for the body to form antibodies. This means that you should not take the test too early – instead you should wait until 2 weeks after you have recovered, or been vaccinated.

Antibodies reduce the risk of falling ill and infecting other

At present, we estimate that almost everyone who has developed antibodies is protected against reinfection. This means that there is lower risk that you will get infected and become seriously ill. You are also less likely to pass the virus on to others.

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Antibodies after you have recovered from a COVID-19 infection

Some people who have had COVID-19 do not get measurable levels of antibodies, while others develop measurable levels that can be detected in a blood sample. A negative antibody test result does not rule out the possibility of a person having had COVID-19. Although not everyone who has been ill with COVID-19 develops measurable levels of antibodies in the blood, in the vast majority of cases these people still develop some form of immune response.

Antibodies after vaccination

There is a difference between the antibodies developed after a COVID-19 infection and those developed after a vaccination against COVID-19. Some antibody tests only detect antibodies after an infection, not after vaccination. If you take an antibody test after vaccination, it is important to make sure that the test used is the kind that detects antibodies specifically developed after vaccination.

Antibody tests in the form of self-tests

There are antibody tests that you can take and read yourself.

The test result from a self-test cannot be used when a certificate is required that shows that you have had COVID-19, or that you have been vaccinated.

Note that not all self-tests are made to indicate levels of antibodies developed after vaccination.