More than 100 scientists have condemned the government's plans to abandon coronavirus restrictions - describing it as a "dangerous and unethical experiment".
In a letter published in The Lancet, they warned any strategy that tolerates high levels of infection is "illogical".
Urging ministers to reconsider the plans, the scientists also claimed that the exponential growth of COVID-19 "will likely continue until millions more are infected, leaving hundreds of thousands with long-term illness and disability".
The letter says: "This strategy risks creating a generation left with chronic health problems and disability, the personal and economic impacts of which might be felt for decades to come."
There are also fears that the strategy "provides fertile ground for the emergence of vaccine-resistant variants".
Prime Minister Boris Johnson has suggested that restrictions could be eased across England on 19 July - however, a final decision isn't going to be made until Monday.
Dr Chaand Nagpaul of the British Medical Association was among the signatories, and the letter warns pushing ahead with this date is both "dangerous and premature".
While 64.6% of UK adults are fully vaccinated, this drops to 50.7% when accounting for children.
International scientists have also expressed support for the open letter. One of them, Professor Eric Topol, said: "The abrupt rise in UK Delta variant cases will not only engender more Long COVID, but has also already resulted in more severe illness, with hospitalisations and deaths.
"Taking more time to further improve vaccination rates should help reduce the toll of this superspreader disease."
Epidemiologist Dr Deepti Gurdasani, a senior lecturer at Queen Mary University, added: "The government has made a deliberate choice to expose children to mass infection, rather than protect them in schools or vaccinate them. This is unethical and unacceptable.
"Our young have already suffered so much in the past year, and are now being condemned to suffer the consequences of this dangerous experiment."
The scientists also say they are concerned that relaxing measures could mean that further disruption to children's education could become more, not less, likely.
That is because transmission would be allowed to continue over the summer - creating a "reservoir of infection" that will accelerate when schools and universities reopen in the autumn.
Mr Johnson said he wanted to move from "government diktat" towards personal responsibility later this month, removing legal requirements for measures such as mask wearing.
Dr Richard Horton, the editor-in-chief of The Lancet, said: "Contrary to the statements of government scientists, there is no scientific consensus over the government's current plans to remove protective mandates on 19 July.
"Instead, there is deep disagreement. Many scientists are sincerely concerned that with sub-optimal double-vaccination numbers and rapidly rising transmission rates, we are at a very dangerous moment in the pandemic. "