How do you become immune to coronavirus?

How do you become immune to coronavirus?

Our immune system is the body's defence against infection and it comes in two parts.

The first is always ready to go and leaps into action as soon as any foreign invader is detected in the body. It is known as the innate immune response and includes the release of chemicals that cause inflammation and white blood cells that can destroy infected cells.

But this system is not specific to coronavirus. It will not learn and it will not give you immunity to the coronavirus.

Instead you need the adaptive immune response. This includes cells that produce targeted antibodies that can stick to the virus in order to stop it and T cells that can attack just the cells infected with the virus, called the cellular response.

Media captionCan you become immune to coronavirus?

This takes time - studies suggest it takes around 10 days to start making antibodies that can target the coronavirus and the sickest patients develop the strongest immune response.

If the adaptive immune response is powerful enough, then it could leave a lasting memory of the infection that will give protection in the future.

It is not known if people who have only mild symptoms, or none at all, will develop a sufficient adaptive immune response.

Understanding of the role of T-cells is still developing.

But a recent study found people testing negative for coronavirus antibodies may still have some immunity.

For every person testing positive for antibodies, it was found two had specific T-cells which identify and destroy infected cells.

How long does immunity last?

The immune system's memory is rather like our own - it remembers some infections clearly, but has a habit of forgetting others.

Measles is highly memorable - one bout should give life-long immunity (as the weakened version in the MMR vaccine does). However, there are many others that are pretty forgettable. Children can get RSV (respiratory syncytial virus) multiple times in the same winter.

The new coronavirus, Sars-CoV-2, has not been around long enough to know how long immunity lasts, but there are six other human coronaviruses that can give a clue.

Four produce the symptoms of the common cold and immunity is short-lived. Studies showed some patients could be re-infected within a year.

But the common cold is generally mild. There are two more troublesome coronaviruses - the ones that cause Severe Acute Respiratory Syndrome (Sars) and Middle East Respiratory Syndrome (Mers) - in which antibodies have been detected a few years later.

"The question is not whether you become immune, it's how long for," said Paul Hunter, a professor in medicine at the University of East Anglia.

He added: "It almost certainly will not last for life.

"Based on antibody studies in Sars it is possible that immunity will only last about one to two years, though this is not yet known for certain."

However, even if you are not completely immune it is possible a second infection would not be as severe.