Britain is set to reach herd immunity against COVID-19 within days marking a "milestone" in the fight against coronavirus, according to scientists.
Real-time modelling carried out by University College London indicates the UK should pass the critical threshold where the proportion of people who have protection against the virus either through vaccination, previous infection or natural immunity will hit 73.4% on Monday, 12 April.
This is the point at which the nation is seen as having reached a tipping point, known as herd immunity, where sufficient resistance is built up within the community to combat the spread of COVID-19, effectively forcing the coronavirus into retreat.
Professor Karl Friston, of UCL, told Sky News: "It’s like a chain reaction. If you remove the opportunity for the virus to spread from one person to more than one person then it will die out."
But warning against any move to speed up the easing of lockdown restrictions in response to reaching herd immunity, he said: "If we let up, that threshold will go up again and we will find ourselves below the threshold and it will explode again."
Referring to the modelling, Prof Friston said: "We do this in an ongoing way every week and this week it portends a herd immunity threshold crossing, which is a milestone in coming out of the epidemic phase of the pandemic.
"This is just a milestone. It’s a nice milestone that is a reflection of the fact that things are going as planned."
He added: "It does suggest that it is unlikely there is going to be a post-summer or autumn surge in fatalities or hospital admissions."
But urging caution, Prof Friston said: "It doesn’t mean to say that we should suddenly change our approach to unlocking or social distancing.
"The herd immunity threshold itself will depend upon transmission risks that depend upon things like social distancing."
Arguing the government’s roadmap out of lockdown "seems to be pitched at about the right level", he said: "If we now suddenly unlocked that would have a profound influence on contact rates, which would actually elevate the herd immunity threshold and we would put ourselves in an uncomfortable position.
"So we have got to come out of this very, very gracefully and slowly and in a context-dependent way that depends upon progressive reduction in the prevalence of infection and that’s going to be a process that takes weeks and months."
Pressed on the issue of herd immunity, Health Secretary Matt Hancock told LBC: "I was told by some scientists that we were going to have herd immunity in May and then in June and then after that.
"What I prefer to do is watch the data. We have set out the roadmap. The roadmap is really clear. It is our route back to normal."
He added: "I think we have taken the right course in plotting our way to freedom and doing it carefully because we want it to be irreversible."