Antibody tests after COVID vaccination

Published on: 23 June 2021

In most places, antibody tests to check your response to COVID vaccination are not routinely available on the NHS. Here, we list a few things to consider before deciding whether or not to pay for a private test.

Spiky blue sphere representing a virus, surrounded by yellow Y-shaped antibodies

Should I have an antibody test?

In most places, antibody tests to check your response to COVID vaccination are not routinely available on the NHS. There are companies that offer private antibody tests. Many of these are available by post. They involve pricking your finger with a small needle and collecting a few drops of blood in a tube. You send the blood sample to a lab to be analysed.

It is a personal decision whether or not you choose to pay for private antibody testing. Here, we list a few things to consider before deciding whether or not to pay for a test.

Different antibody tests measure different things

The antibodies your immune system makes if you’ve had COVID-19 in the past are not the same as the antibodies your immune system makes after you’ve been vaccinated.

Some tests only check for antibodies from previous infection. These are sometimes called an ‘anti-N’ test because they test for antibodies that react to a part of the coronavirus called the nucleocapsid. Some tests check for antibodies from either previous infection or vaccination. These are sometimes called an ‘anti-S’ test because they test for antibodies that react to the spike protein. Some tests check for anti-N and anti-S antibodies. If you decide to get an antibody test, make sure you order one that is testing the right thing. Check the test information. It should say if it measures antibodies from vaccination or from previous infection. It might say what antibody it checks (anti-S or spike antibodies for vaccination response).

It is also important to remember that antibody levels change over time. It usually takes 2 to 4 weeks after vaccination for antibody levels to peak and then they gradually go down. Scientists don’t know yet how long the antibody response to vaccination lasts, or how this relates to your overall protection from COVID-19.

Antibodies are only one part of your immune response to vaccination

Different COVID vaccines work in different ways, but they all aim to train your immune system to recognise and remember coronavirus. Two main types of cell are important in your immune response to vaccination: B cells and T cells.

  • Some B cells respond by making antibodies straightaway. Some B cells do not make antibodies straightaway but are programmed to remember the virus so they can make lots of antibodies quickly if they come across it again. These are called memory B cells.
  • Some T cells respond by making substances that aim to kill the virus. Some T cells respond by activating B cells and telling them to make lots of antibodies. Some T cells are programmed to remember the virus so they can respond quickly if they come across it again.

Antibody tests check whether or not your B cells made antibodies straightaway in response to vaccination. They do not measure your memory B cells or test whether your T cells have responded.

T cell responses are much harder to measure than antibodies. Tests of T cell response are not routinely available, either on the NHS or privately, although they are used in some clinical trials.

Scientists don’t know yet what antibody test results mean in terms of your protection against COVID

Some antibody tests tell you if you have made antibodies or not, but don’t tell you how many you have made. You might get a positive result even if you have made very few antibodies. Other tests measure the exact level of antibodies you have made.

At the moment, scientists don’t know how antibody levels relate to your overall protection from COVID-19. Low antibody levels might still offer useful protection, while normal antibody levels do not guarantee complete protection. Having a negative antibody result doesn’t necessarily mean you haven’t responded to vaccination – you might have a T cell response that may provide some protection. Antibody testing does not measure this T cell response.

Many people with lymphoma are able to generate an antibody response after COVID-19 vaccination and this is likely to be better than not having an antibody response. However we really don't know what a negative antibody result means, given that this is only measuring one part of an immune response. There may be some protection but this requires further research.

Professor Tim Illidge, Professor Of Targeted Therapy and Oncology, The Christie Hospital, Manchester

Healthcare professionals base their advice on your individual circumstances, not your antibody response

Haematology specialists we spoke to felt that antibody testing was not generally helpful for people with lymphoma. This is because, regardless of your antibody levels, your medical team base their advice on your individual circumstances. When they recommend steps you should take to reduce your risk from COVID-19, they consider factors such as:

  • your age
  • your type of lymphoma and any other illnesses you have
  • whether you are on, or have recently finished, treatment
  • the level of COVID-19 infection in your area
  • how much contact you have with other people at home, socially and at work
  • your personal risk of becoming severely ill if you do get COVID-19
  • your mental wellbeing.

It is sensible to be cautious as society opens up, but it is unrealistic to expect people to shut themselves away. We advise people on a case-by-case basis depending on their personal risk. As more research becomes available, we will be able to offer even more tailored advice.

Dr Shirley D'Sa, Consultant Haematologist, University College London Hospitals, London

Helpful resources

We appreciate that this might be a worrying time. If you’d like to talk, contact our Helpline Services on freephone 0808 808 5555 from 10am to 3pm, Monday to Friday, or via Live Chat through our website. You can also email us at information@lymphoma-action.org.uk.

You might find some of our other resources helpful:

23 June 2021