The UK's chief scientific adviser has said the government wants 60 per cent of the population to catch coronavirus to try and create “herd immunity” to protect against the virus becoming an annual crisis.

Sir Patrick Vallance told BBC Radio 4’s Today Programme that he thought the coronavirus was likely to become an "annual virus" and that the strategy was to limit the impact on the NHS but not stop the virus completely.

He said: “What we don't want is everybody to end up getting it in a short period of time so we swamp and overwhelm NHS services - that's the flattening of the peak," he said.

"You can't stop it, so you should end up with a broader peak during which time you'd anticipate that more people would get immunity to this. That in itself becomes a protective part of this process.

"This is quite likely, I think, to become an annual virus, an annual seasonal infection."

He later told Sky News: "Communities will become immune to it and that's going to be an important part of controlling this longer term.

"About 60 per cent is the sort of figure you need to get herd immunity."

In a situation where infection is uniform across the country this could equate to around 39 million people becoming infected. According to earlier modelling by the World Health Organisation a mortality rate of 1 per cent would mean 398,000 people dying from coronavirus and potentially 1.9m people becoming critically unwell and needing hospital treatment.

It is not clear what the actual death rate for the virus in the UK, and experts have suggested it may be much smaller than one per cent. Many people with mild symptoms may not ever be cofirmed to have the virus and are not counted in the mortality rate calculations which would be lower if they were.

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Sir Patrick told the BBC that the advice the government is following for tackling coronavirus is not looking to "suppress" the disease entirely but to help create a "herd immunity in the UK" while protecting the most vulnerable from it.

Asked if there is a fear that clamping down too hard on its spread could see it return, Sir Patrick said: "That is exactly the risk you would expect from previous epidemics.

"If you suppress something very, very hard, when you release those measures it bounces back and it bounces back at the wrong time.

"Our aim is to try and reduce the peak, broaden the peak, not suppress it completely; also, because the vast majority of people get a mild illness, to build up some kind of herd immunity so more people are immune to this disease and we reduce the transmission, at the same time we protect those who are most vulnerable to it.

"Those are the key things we need to do."

Sir Patrick said some of the social distancing measures put in place by the government, including self-isolating for seven days if symptoms develop, are "actually quite extreme".

Sir Patrick said it was "eye-catching" to order the cancellation of mass gatherings and sporting events but that the chances of contracting the disease by attending such occasions are slim.

He told the BBC: "Mass gatherings do have some impact, it is not that they don't do anything if you stop them.

"But they are very much more minor than the other ones.

"The most likely place you are going to get an infection from is a family member, a friend, someone very close in a small space, not in the big space.

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"It is sort of eye-catching to say 'Stop those' (but) it is not actually a big effect on the transmission.

"That is not to say we wouldn't do it at some point but it is not the most important thing to get into place first."

He said those watching the Wales v Scotland Six Nations rugby tie in pubs are more likely to contract the illness than those in the Principality Stadium on Saturday.

"I think it is more likely that there will be transmission in pubs and other areas where people are aggregating watching it than in the actual stadium itself.”

He did not, however, urge people to stay out of pubs or social situations as a result, only repeating advice that those with symptoms should remain at home.