What are COVID-19 antibody tests, how do they work, and why should you do one?

When our bodies come under attack from a virus, they produce antibodies to help fight it. This is a normal part of the body's immune response and happens constantly.

Sometimes we know we have been infected, as we suffer the effects of a virus in terms of symptoms; but other times we don’t. This has been a puzzling effect of the Coronavirus. In fact, one of the most surprising things about COVID-19 is that it is present in so many people without evidence of the three main symptoms at all (cough, fever and loss of taste or smell). One study of 36,000 people undertaken by University College London revealed that 86% of people who tested positive for COVID-19 did not have any of the three main symptoms. A majority of carriers are asymptomatic and this has been one of the drivers of the spread of the virus. 

Now, there are many other symptoms of COVID-19, ranging from “COVID toe” to diarrhoea, that may be exhibited. But the point is that there are so many ways in which COVID-19 presents itself in the body that it can be impossible to tell whether someone has had it or not, if they did not have a test at the time. This was especially difficult for people that had been infected in the early days of the pandemic, before testing was widespread and readily available.

Do antibodies confer immunity against the Coronavirus?

Although England has reported 3 million cases of COVID-19, the Office for National Statistics estimated that one in eight people in England – or 6.6 million people – had antibodies in December 2020, which implies that the number of people who have had the virus is more than twice the number who have received a positive test.

The good news about antibodies is that they tend to provide a degree of long-term immunity to a virus. For most of the past year, governments globally have been reluctant to confirm that COVID-19 antibodies confer immunity because they didn’t want it to change people’s behaviour. 

How long does immunity last?

Recently, however, a major study undertaken by Public Health England has confirmed what many people have been arguing for a long time – that COVID-19 antibodies do confer immunity for many months. The PHE study says it’s around five months of immunity; whereas an antibody study conducted in South Korea estimated it to be around eight months.

Rather than argue over whether the immunity response lasts five or eight months, the positive news is that governments have finally accepted that antibodies do give a level of immunity to COVID-19.

How do antibody tests work?

Testing for antibodies is straightforward and most commonly done by taking blood – through veins or finger-prick – and analysing it in a laboratory or using a rapid testing device. It is quick, simple and relatively painless.

Confirm Testing offers an at-home service that allows people to take a small amount of blood using a finger-prick lancet and then send it off the laboratory for analysis, with results coming back about 24 hours later. It’s a really easy product to use and gives accuracy of almost 100%. 

We will shortly be offering a rapid antibody test from our clinic at 1 Harley Street where a trained NHS nurse will place a small amount of finger-prick blood onto a testing “cassette” that will return a result within about 15 minutes. Accuracy is 99%.

Why should you do an antibody test?

COVID-19 antibody tests are especially useful to people that suspect they've had the infection but were unable to get tested while they had the live infection. This tests helps you confirm your status. 

It's also especially useful if you're awaiting your turn in the vaccination schedule and want to know if you have a level of immunity until then. 

Knowing if you’ve had the virus and have got antibodies has always been of great interest to many people; but now it can could be as useful as having had the vaccine while you wait your turn for the vaccine itself.