Coronavirus immunity: what do we know?

What does scientific research say about coronavirus immunity? In this article we explain what we know so far about whether you are immune to coronavirus after you catch it, what coronavirus antibodies and what antibody tests mean for future coronavirus control and prevention.
Coronavirus vaccine ingredients

Are you immune to coronavirus after you catch it?

There is still a lot of uncertainty surrounding the novel coronavirus, and as a result there is not yet a scientific consensus as to whether people gain complete immunity after they catch it.

Some people who have beaten the virus do not have antibodies in their blood, whereas others develop antibodies that cannot effectively neutralize the virus. This means that we can’t know for sure if a person is immune to the disease, we only know if a person has previously been infected.

SARS-CoV-2 image from a scanning electron microscope

Can you catch coronavirus twice?

Without any conclusive evidence it is not yet possible to say whether people can catch coronavirus again. However, in the case of previous coronaviruses, reinfection was possible after about a year, suggesting that it is possible that recovering from infection could offer a short period of immunity.

Antibodies are a type of blood protein that the body develops to help it fight infection. People who have overcome an infection usually have the specific antibodies for that disease in their blood.

Antibody treatment vs vaccine

Antibody treatments are where patients are injected with specific antibodies to help treat coronavirus infection. This can either be in the form of synthetic antibodies, or in blood that has been taken from patients who have overcome coronavirus infection. Giving patients antibodies helps them to fight coronavirus while their body begins to produce their own antibodies.

Treatment with blood transfusion is called plasma therapy, and there is currently a trial underway in the UK to examine its effectiveness.

Blood donation for plasma therapy, one of the treatments being tested for effectiveness on coronavirus patients

Another method for antibodies to treat coronavirus patients is to create synthetic ones in a lab. Treatments which involve creating synthetic antibodies are underway in a number of countries all over the world.

By contrast, a vaccine does contain antibodies, but instead the “instructions” for your body to make coronavirus antibodies itself.

How do coronavirus antibody tests work?

Antibody tests check if you have antibodies in your blood. This means that the antibody test can show whether you have previously been infected with the novel coronavirus.

Antibody tests for coronavirus vary in terms of the method used to check for antibodies in the blood.

Some coronavirus antibody tests rely on blood samples

If my antibody test is positive, am I immune?

A positive result from an antibody test means that you have antibodies in your blood and indicates you have previously been infected with coronavirus. It does not, however, mean that you are necessarily immune to the disease.

It is also important to bear in mind that there are different tests with different specifications and accuracy levels. There is also a potential risk for a false positive on an antibody test, and you should not change your behaviour just because you test positive, as it might not mean you are immune.

How much of the UK population has coronavirus antibodies?

Estimates for how much of the UK population have coronavirus antibodies vary widely. In a recent study from Imperial College London, researchers estimated that between 0.5 - 15% of the population have antibodies for coronavirus, depending on location.

How could antibody tests help fight coronavirus?

Antibody tests can help create a clearer picture of how coronavirus spreads, allowing health authorities to understand better how infection is happening within communities. As antibody tests reveal which people have been previously infected, results can also tell us more about how the body’s immune system responds to the coronavirus. If treatments such as plasma therapy are proven to be effective, antibody testing could also identify possible plasma donors.

Antibody tests for coronavirus can help scientists understand how the virus is spreading through communities.

How accurate are the antibody tests?

With a big increase in the demand for antibody tests, there has also been a large increase in the number of tests on offer to the public. Some tests are less reliable than others. It is important research how accurate and reliable a test is before you get it.

If the antibody test used has a high accuracy, the test result can be trusted to a certain extent. With a high accuracy, there will be a very low chance that the test will show a false positive result.

Will there be “immunity passports” for people who have positive antibody tests?

Since we still don’t know much about immunity, it would be unwise for governments to focus on so-called “immunity passports”. When there is still so much doubt around accuracy standards for tests, and whether people can become immune to coronavirus, allowing greater freedoms to those with positive antibody tests could put both the individual in question and greater society at risk. The World Health Organization has highlighted concerns about the concept of immunity passports and advised against governments adopting the policy.

As we still aren’t certain that you can’t catch coronavirus twice, it would be risky to implement any kind of immunity certificate. Many countries also currently have a very low level of immunity, as in places like Norway, where less that 1% of the population are estimated to have caught coronavirus already.