What is the immune system?

The immune system is the body's natural defence to illnesses - it's a complex network of cells and proteins working to build up defences when an infection enters our body.

"Injury, infection and even cancer leave signals that are identified by the immune system that continuously polices the body," Dr Barnish says.

"The different cells of the immune system mask appropriate defensive responses, usually resulting in inflammation. Incredibly, the immune system has a capacity to remember what the best methods were to attack previous invaders so that a future exposure will be much less problematic. This is how immunity is built up and the basis of how vaccines work."

The body's inflammation response is caused by our innate immune system, Dr Macciochi adds, but sometimes extra back-up is needed from the adaptive immune system. The innate immune system offers an immediate, but nonspecific reaction to illness or injury. The adaptive immune system takes longer to respond but is a lot more targeted in its attack.

"The adapted immune response is highly specific: it takes up to five days to prepare an army of cells and antibodies to deal with the infection. Adaptive immunity also involves a memory response that remembers the specific germ and protects us if we are ever exposed to it again," she explains.

"This is also the principle of vaccination. But it doesn't work for all germs. For example, most of us will get chickenpox as a child which will result in a memory response that protects us for the rest of our lives. This doesn't work with the common cold. That's because the rhinovirus, which is responsible for the common cold, is always slightly changing its surface patterns to evade our immune memory."

Immunity against COVID-19

Unfortunately, as the COVID-19 strain of coronavirus is still so new, it's not yet known whether our bodies will build up an immunity to the virus.

"We do not know enough about the interaction between the current coronavirus and our immune system to definitely say if we would develop a protective immune memory response," explains Dr Macciochi.

"And if we do, we don't know if the memory response is long-lived. Nor do we know whether the virus will mutate and evade that protective memory."

But there is some good news. As people are recovering from COVID-19 it suggests our bodies are capable of an immune response to the virus.

"We know, with many people recovering from coronavirus, that the immune system can successfully fight off the COVID-19 virus. Evidence of the role each immune cell type plays is emerging. There are some similarities being observed to the flu virus response," Dr Barnish adds.

"Our bodies will have the capacity to build immunity to COVID-19, if exposed. However, like many viruses, this coronavirus can change easily and often. A new version of the virus may have the ability to hide from the immune memory cells. This is why influenza vaccines need to be given each year (rather than just a few times in a lifetime), to keep up with these changes."