Prof James Naismith, Director of the Rosalind Franklin Institute, said the current growth in cases is "unsettling" amid the perceived expectation that younger unvaccinated people should "get on with it".
Prof Naismith was commenting on the latest Office for National Statistics (ONS) infection survey, which estimated 211,100 people in England had COVID-19 in the week up to Sunday. This was up from 122,500 in last week’s survey.
On Friday, the prime minister reiterated his intention to end England’s lockdown as planned on 19 July, though he also suggested on Thursday it will be done so with "extra precautions".
Watch: PM hints 'extra precautions' still needed after 19 July
Johnson has cited the effectiveness of vaccines, with the exponential growth in cases – driven by the 60% more infectious Delta variant – not having translated into huge numbers of hospital admissions and deaths.
While 63% of the adult population has been double vaccinated, Our World in Data figures show more than half - 51% - of the total population has not yet received both jabs. Vaccines are only available for over-18s.
Prof Naismith said: "The government commitment to release restrictions on 19 July means the rate of growth of infections will accelerate.
"It seems now unavoidable that Delta will sweep through the unvaccinated: mainly young. Although young people are at much less risk, it’s not zero. A wave on the scale of what now seems likely will result in lives being blighted.
"One view, which I have disagreed with, was since COVID ‘mainly’ affects old people, it does not matter so much. This seems to have been replaced with 'now the old are vaccinated, the young can get on with it' – which I find equally wrong.
“Only young children seem to be at almost zero risk. In any event, we are conducting the experiment so we will undoubtably know the truth of this.”
Prof Naismith added the UK’s "point of maximum danger has probably passed, although I remain very concerned about the harm for younger people".
His warning came after Scientific Advisory Group for Emergencies (Sage) adviser Prof Mark Woolhouse also said: "We have the biggest Delta outbreak in a well-vaccinated country. We are a petri dish for the world."
On Friday, the government announced there had been 157,675 COVID cases in the past week, up 74% on the previous seven-day period.
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