Many people will have come into contact with Covid-19 since the beginning of the pandemic in March 2020.
However, some people have reported being infected with Covid not once but twice.
Getting Covid multiple times is indeed possible, and now that the Omicron variant has become dominant, the chances of reinfection are even higher.
The UK Health Security Agency carried out a study which found that one in ten people in the UK with Omicron had previously been infected with Covid.
The study found that previous Covid infections provided little protection against the Omicron strain.
Researchers at Imperial College London found that Omicron mostly evaded immunity from past Covid infection.
A study of all the PCR tests in the UK over two weeks found that those who had been infected with Covid previously had around 20 per cent protection from Omicron.
This was in line with two doses of a Covid vaccine, which scientists estimated were as much as 20 per cent effective against the new variant.
The data emphasised the importance of getting the booster jab which is said to increase protection to 55 to 80 per cent.
Can you get Omicron twice?
Most public health bodies define reinfection as two positive Covid test results over 90 days apart.
The reason for this is that after testing positive for Covid residual signs of the infection can show up for three months on a PCR test.
There is not enough data on the Omicron variant just yet to determine if reinfection of the strain is likely.
However, some health bodies say it is possible to get Omicron more than once as it is possible to get any Covid variant several times.
How long after getting Covid can I be reinfected?
For most people who have recovered from Covid, immunity can last for about three months and longer in some cases. However, experts have said it is possible that some may get reinfected sooner than this.
Dr William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Centre: "There are some people who have the notion that after you've gotten a natural infection, you will be permanently protected against Covid-19 as if this were measles.
"But the two viruses that cause these infections are very, very different. The coronavirus protection wanes naturally after a period of time."
