The idea that herd immunity can be achieved with a coronavirus vaccine is "mythical", the UK's top vaccine boss has warned.
Professor Sir Andrew Pollard, director of the Oxford Vaccine Group, said on Tuesday that herd immunity is “not a possibility” with the current Delta variant.
He called the idea “mythical”, warning that vaccine programmes should not be developed around it.
“We know very clearly with coronavirus that this current variant, the Delta variant, will still infect people who have been vaccinated and that does mean that anyone who’s still unvaccinated, at some point, will meet the virus,” Pollard told a session of the All-Party Parliamentary Group (APPG) on coronavirus.
He said that while vaccines might “slow the process” of transmission down, they cannot currently stop the spread completely.
“I think we are in a situation here with this current variant where herd immunity is not a possibility because it still infects vaccinated individuals,” he said, predicting the next thing may be “a variant which is perhaps even better at transmitting in vaccinated populations”.
He added: “So that’s even more of a reason not to be making a vaccine programme around herd immunity.”
The APPG session also heard that variants that could escape protection of the vaccine are an "absolute inevitability", according to Professor Paul Hunter, from the University of East Anglia.
He said the seasonal coronaviruses in circulation will infect people “repeatedly” throughout their lives, typically on average every four or five years.
Watch: More than three-quarters of UK adults have now had two COVID jabs
“Quarter of the UK population will get infected on average every year, what that means is about 45,000 people will be infected every day with theses other coronaviruses.
“Ultimately what happened with these other coronaviruses is that although you get a gradual escape, because we are getting re-infected so frequently, we actually keep up.”
His comments came after renowned US epidemiologist Dr Larry Brilliant said there is a low probability that a "super variant" resistant to vaccines would emerge.
Brilliant added that the world should still do “everything possible” to prevent such an outcome, saying: "That means get everyone vaccinated – not just in your neighbourhood, not just in your family, not just in your country, but all over the world."
According to Office for National Statistics (ONS) estimates, the percentage of adults who would test positive for coronavirus antibodies has continued to increase across the UK up to the week beginning 12 July.
The percentage of adults who reported they had received at least one dose of a COVID vaccine ranged from 88% to 91.8% in the UK in the week beginning 12 July, the ONS figures show.
Meanwhile, the estimated percentage of adults who are fully vaccinated continued to increase, ranging from 68.5% to 76.9%.
It comes as health secretary Sajid Javid said preparations are being made to offer COVID booster jabs from next month.
He said on Tuesday: “When it comes to booster jabs we are waiting for the final advice from JCVI, that’s our group of independent clinical advisers, and when we get that advice we will be able to start the booster programme, but I anticipate it will begin in early September, so I’m already making plans for that.
“It’s really important that when we start that programme, the sort of first cohorts, the ones that got the jabs early on when we started our programme – the first in the world back in December last year – that those cohorts come first and so we will be prioritising it.
“Also in terms of vaccination, it’s important to say that they’re working. This wall of defence that the vaccines have created are working.
"It’s massively reduced hospitalisations, deaths from COVID are mercifully low and that’s because of our vaccination programme.”
He also said the plan is for the flu jab to be offered, especially to over-50s, at the same time as the COVID booster jab.
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