Coronavirus antibody tests: what they are and how they work

Why do we need an antibody test?

An antibody test is often described as the “have you had it?” test, as it reveals whether a person has had the coronavirus. The results are valuable for a number of reasons. At the population level, antibody tests give a picture of how widely the virus has spread. More people with antibodies means a lower risk of a second wave of infections when the lockdown is eased, since the antibodies are expected to confer at least some resistance.

The number also sheds light on the lethality of the disease, giving doctors an indication of the infection fatality rate – the risk of death from picking up the virus.

 Coronavirus tests: how they work and what they show

The tests are less helpful on the individual level, but can potentially tell who has been infected and had an immune response and who hasn’t. But tests would need to become much more accurate, and the level of protection better understood, for them to be used for the much-mooted idea of “immunity passports”.

Will a test tell you if you are immune?

No. The antibody test is just that – it reveals if your body has antibodies, which means you have encountered the coronavirus.

Speaking to MPs on the health and social care committee on Tuesday, Sir Patrick Vallance, the government chief scientific adviser, said current evidence suggested the vast majority of people who have had an infection got some form of antibody response. But he said it was not yet clear whether asymptomatic cases got as strong a response.

What these antibodies mean for immunity is still being unpicked.

“Everything suggests that you can get neutralising antibodies. Those are antibodies which protect against the disease,” said Vallance.