A doctor has explained why some people suffer repeat bouts of coronavirus whereas others seem to escape it completely.

Leading GP, Dr Alan Stout, commented on reinfection after Labour leader Sir Keir Starmer shared that he tested positive for the second time this week after an initial infection in October 2021.

It is also his sixth period in isolation since the pandemic began, reports Belfast Live.

READ MORE: Free Covid lateral flow tests will 'absolutely not' be scrapped says Education Secretary

But while some people seem to repeatedly catch coronavirus, others remain immune.

Dr Alan Stout, chair of the British Medical Association's GP committee in Northern Ireland, said people "can absolutely get Covid twice" and it explains why case numbers here remain high.

On Friday morning, there were 402 Covid-positive patients in hospital, of whom 31 were in intensive care.

Dr Stout told Belfast Live : "The vast majority of people we're seeing in the daily figures will have had some sort of previous infection.

"Keir Starmer is a good example as what he will have now is almost certainly the Omicron variant and previously, he may well have had the Delta or Alpha variant.

"One of the difficulties with the variants is that having one of the previous ones doesn't necessarily protect you from the next. That has become quite clear as the previous Delta infection we know now gives you virtually no protection or natural immunity from Omicron.

"That's the simplest reason why people are contracting Covid twice - it's down to the different variants."

While cases of people catching Covid-19 more than once have been reported throughout the pandemic, concern is growing as immunity wanes and new variants emerge.

Dr Stout added: "That's why the booster has been so important for Omicron because we've known that the level of immunity given by the first two vaccine doses has started to wane.

"Hence the booster was giving that extra level of protection but it was actually giving protection above and beyond, which is then preventing people getting Omicron or certainly becoming seriously unwell with it."

But Dr Stout said research around reinfections is still in its infancy.

"That's one of the things we're learning as we go along and yet there is quite a lot of data and evidence around what protection people have, which then helps with the planning in terms of vaccination.

"One of the big things we don't know is around any next variant. Equally while we know there will definitely be more variants, whether we get a more severe one or they become less and less severe with time and evolution is another significant possibility."

Receive newsletters with the latest news, sport and what's on updates from the Liverpool ECHO by signing up here