This test result means that we were unable to detect antibodies to coronavirus in your dried blood spot sample. There are a few reasons this might be.
1. No test is perfect – so it is possible that you have antibodies, but our test failed to detect them. We know that the antibody test is negative in 3.7% of people who have had a proven coronavirus infection.
2. You might have done your fingerprick test a long time after getting the vaccine – so your antibody response might have faded by the time you gave your blood spot sample.
3. You might be taking medicines that suppress the immune system – they could interfere with your body’s ability to mount an antibody response after vaccination.
4. You might have a medical condition that affects the immune system’s ability to respond to vaccination.
We do not yet know whether a lack of antibodies after vaccination is associated with an increased risk of COVID-19 down the line – indeed, this is one of the main questions that our research is designed to answer.
It is important to remember that antibodies are just one part of the protective immune response that is induced by vaccination. Vaccination can also induce protective T cell responses, and our antibody test does not measure these. We know that some people develop T cell responses, but not antibody responses, after coronavirus infection – and this may also be the case following vaccination. (We are studying T cell responses in a small group of COVIDENCE participants to address this question – but the T cell test cannot be done on a dried blood sample unfortunately).
We are not routinely informing participants’ GPs about their antibody test results, as our test is a research test, not a routine clinical test – i.e. we do not yet know the clinical significance of having a negative result from our antibody test after vaccination. However, you may well want to let your GP know your result, as they may advise that you have a different type of vaccine to the one you originally had if you have a booster shot at some time in the future. (Since the Astra Zeneca and Pfizer vaccines work in different ways, it is possible that some people will respond better to one type of vaccine more than another).
Your negative antibody test result suggests that you have probably not been infected with the SARS-CoV-2 coronavirus in recent months. If you definitely had COVID-19 in the past, and your antibody test is negative now, it might be that your antibody response has faded or ‘waned’ since your illness. This is more common in people who have had relatively mild COVID-19. Immunosuppressant medications or medical conditions affecting the immune system can also dampen the antibody response to coronavirus.
Your negative antibody test result suggests that you were probably not infected with the SARS-CoV-2 coronavirus in the months before you were vaccinated. If you definitely had COVID-19 before you were vaccinated, it might be that your antibody response faded or ‘waned’ between the time of your illness and the time when you did the fingerprick antibody test. This is more common in people who have had relatively mild COVID-19. Immunosuppressant medications or medical conditions affecting the immune system can also dampen the antibody response to coronavirus.
Vaccination should stimulate an antibody response, which would be detected by our test. However, there are a few reasons why your antibody test might be negative even though you have had a COVID-19 vaccine:
It’s important to remember that our test only detects one part of the protective response to the coronavirus – the B cell response. Vaccines also stimulate protective T cell responses, which aren’t picked up by our test (you need a fresh blood sample to detect them, so a dried blood spot can’t be used). It may be, therefore, that the vaccine is still giving you protection even if your antibody test is negative.
Vaccination should stimulate an antibody response, which would be detected by our test. There are a few reasons why your antibody test might be negative even though you took part in a COVID-19 vaccine trial:
Your positive antibody test result suggests that you have probably been infected with the SARS-CoV-2 coronavirus at some time in the last few weeks or months. The presence of antibodies does not guarantee immunity to COVID-19 in the future, so you should continue to follow government guidance to minimise your risk of future infection. The presence of antibodies does not remove the need for vaccination, which is likely to offer additional protection over and above that provided following natural infection.
Your positive antibody test result suggests that you were probably infected with the SARS-CoV-2 coronavirus before you were vaccinated. Government guidance is that people who are offered the vaccine should have it, even if they had COVID in the past – so you should rest assured that were given the vaccine appropriately.
Your positive antibody test result shows that your body has mounted a successful immune response to the SARS-CoV-2 coronavirus following vaccination. The presence of antibodies does not guarantee immunity to COVID-19 in the future, so you should continue to follow government guidance to minimise your risk of future infection.
Your positive antibody test result shows that your body has mounted a successful immune response to the spike protein on the SARS-CoV-2 coronavirus. This could be as a result of vaccination against COVID-19, or as a result of ‘natural infection’ with the SARS-CoV-2 coronavirus. You will not be able to tell which until you find out whether you received vaccine or placebo [dummy injection] in your clinical trial.
Yes, the vaccine can be given if you have had a positive antibody test.
Our first round of invitations to have antibody testing have all gone out now, but we are planning a second wave of antibody testing in Summer 2021. If you would like to be invited to have an antibody test in the future, please sign up to take part in the COVIDENCE UK study at www.qmul.ac.uk/covidence.
More information is available here and here.
False-positive results are rare: just 0.7% of people who did not have COVID-19 had a positive antibody test (more information here).
It is not uncommon for someone to have asymptomatic SARS-CoV-2 infection, and this a more likely explanation for a positive test in somebody who never had COVID-19 symptoms.
Yes, but they are not common: just 3.7% of people who had mild or moderate COVID-19 had a negative antibody test afterwards, using this test (more information here). Most often this arises because the COVID-19 occurred several months prior to the antibody test; we know that antibody responses can wane over a period of months.
Yes: we would expect somebody who has had the vaccine to have a positive antibody test within a few days of vaccination.
We will use test results from vaccinated people to investigate factors influencing the response to vaccination, and to determine the extent to which having antibodies after vaccination can protect against subsequent risk of COVID-19.
No, we are not forwarding results to participants’ GPs. This is because the antibody test is currently being used as a research test only.
Antibody test results from unvaccinated people tell us about whether or not a person had ‘natural’ infection with SARS-CoV-2. This information will be used in our analysis of risk factors for COVID-19.
No - please do not give your kit to someone else. Your blood spot card bears a barcode that will link the result to your questionnaire data in the COVIDENCE database. If the test result is from somebody else, this will introduce inaccuracies in our data and compromise the scientific value of our study.
Please post it back to us unused in the pre-paid envelope provided. Please do not give it to somebody else to use.
Yes: we have applied for funding to do another round of antibody testing in Summer 2021.
Unfortunately turnaround times are longer than anticipated, due to pressures on our laboratory arising as a consequence of the pandemic. We are doing our best to get your result to you as soon as we can: thank you for patience and understanding during this very challenging time.
Please email covidence@qmul.ac.uk and we will send you a replacement.
As long as there is at least one small blood drop on the card, we will do our best to get a result from it. Please post it to us and we will get back to you to offer another kit if the sample is too small to use.
Please email covidence@qmul.ac.uk and we will do our best to help, sending a replacement kit if necessary.