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Explains antibody testing for COVID-19 including that it cannot tell people whether they are immune.

First published:
29 June 2020
Last updated:

What is COVID-19 Antibody testing?

COVID-19 antibody testing measures the amount of COVID-19 antibodies in a blood sample.

It was first used to find out whether a person had already had the virus. This helped us understand how the disease was spreading. They can now also tell us if someone has had a coronavirus vaccination.

Antibody tests are different to antigen (swab) tests which see if you currently have the virus.

The body's immune system produces antibodies when it detects harmful substances, called antigens. When a person has COVID-19 (the antigen) it produces COVID-19 antibodies. Antibodies recognize and latch onto antigens to remove them from the body. The antibodies produced for each antigen are unique, hence the term COVID-19 antibodies.

Since December 2020 we have been vaccinating people across Wales. Vaccination produces antibodies in the blood that can detect and neutralise the antigen.

Before December 2020 COVID antibodies were only found in people with the disease.

Since December 2020 the presence of antibodies in a person’s blood sample could either be due to:

  • previous infection
  • vaccination or both

Antibody tests are now able to detect two different types of antibodies:

  • ‘n’ antibodies (necleocapsid) which appear after an infection
  • ‘s’ antibodies (spike antibodies) which appear after an infection or vaccination

COVID-19 antibody testing measures the amount of COVID-19 antibodies present in a blood sample.

They were first used to find out whether a person had already had the virus and helped us understand how the disease was spreading. They can now also tell us if someone has had a coronavirus vaccination.

Antibody tests are different to antigen (swab) tests which see if you currently have the virus.

An antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. When a person is infected by COVID-19 (the antigen) it produces COVID-19 antibodies. Antibodies recognize and latch onto antigens in order to remove them from the body. The antibodies produced for each antigen are unique, hence the term COVID-19 antibodies.

Since December 2020 we have been vaccinating people across Wales. Vaccination works in a number of ways but one of the things it does is to produce antibodies in the blood which are ready to detect and neutralise the antigen if it appears.

Before December 2020 COVID antibodies were only found in people who had been infected with the disease. Since December 2020 the presence of antibodies in a person’s blood sample could either be due to previous infection or vaccination or both.

Antibody tests are now able to detect two different types of antibodies - n antibodies (neucleocapsid) which appear after an infection and s antibodies (spike antibodies) which appear after an infection or vaccination.

The value of antibody testing

Antibody testing tells us how many people have had the infection and how far and wide the virus has spread. It also reflects how many people have had the vaccination.

There is currently not enough evidence on how well COVID-19 antibodies are at:

  • fighting the virus
  • protecting you from getting it again
  • stopping transmission to others

We also don’t know how long antibodies from the infection will last. As scientific evidence and research improves this should provide answers to these questions.

Antibody testing tells us how many people have had the infection and how far and wide the virus has spread. It also reflects how many people have had the vaccination.

We don't know enough yet about how effective antibodies from the infection are at getting rid of the virus. Whether they will protect you from getting it again, or whether you can’t pass the virus on to others. We also don’t know how long antibodies from the infection will last. As the scientific evidence and research grows we hope to have the answers to these questions.

Who can get an antibody test in Wales

We are not currently offering antibody tests. This is because we use other studies to understand infection and vaccination. Your doctor could still offer you an antibody test for medical purposes.

Between June and November 2020 antibody testing was conducted on:

  • some healthcare workers
  • social care workers and residents
  • teachers and pupils in the education hubs

This was to help us understand if and how they got the virus. We continued testing domiciliary care workers until April 2021. They now have regular COVID-19 tests and are being vaccinated. This means we do not need to continue antibody testing.

Random samples of the population have tests for COVID-19 antigens. This will provide a picture of the prevalence of COVID-19 in the UK population. We publish statistics for Wales every month.

UK research projects are testing how antibodies from infection or vaccination differ across groups of people and over time. This will help to understand how long infection and vaccination can give protection.