Boris Johnson's scientific advisors have warned that Covid cases could rise "rapidly" as isolation ends and free tests are scrapped.
The Prime Minister plans to end mandatory isolation for people with Covid from Thursday - but the warning was issued more than two weeks before the announcement and was only published on Friday.
The Scientific Advisory Group for Emergencies (SAGE) said transmission could rise by between 25% to 80% if Brits "return to pre-pandemic behaviours and no mitigations", the Mirror reports.
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They added: "Warwick’s analysis indicates that, while behaviour change following the lifting of restrictions has previously been gradual, a sudden change, such as an end to testing and isolation, has the scope to lead to a return to rapid epidemic growth."
The Prime Minister will unveil a ‘Living with Covid ’ plan for England on Monday.
He is also tipped to announce a future date for end of free Covid tests. And he is weighing up whether to scrap £500 isolation payments and sick pay from day one.
The Scientific Pandemic Influenza Group on Modelling (SPI-M-O) delivered its conclusions on February 2.
But Boris Johnson announced on February 9 his "expectation" to "end the last domestic restrictions" this month.
SPI-M-O said experts were "considering how behaviour is likely to change in the medium to long term" as restrictions are eased.
Other factors that effect the transmission rate, either way, include waning immunity, new variants, the seasons and vaccine protection as more get the jab.
In a separate report on February 10, SAGE group NERVTAG warned it was a "realistic possibility" that the next major Covid variant could be more deadly, not less.
It added: "The loss of virulence as viruses evolve is a common misconception."
NERVTAG also said it was a "realistic possibility" that a new variant will evade vaccines, or that the virus will retreat into animals, evolving further before breaking out into humans again.
And the group said it is "almost certain" that the virus will continue to evolve in a way that "eventually leads to current vaccine failure".
The "worst case" is that it becomes difficult to re-vaccinate people because people’s immune response is dominated by previous strains, NERVTAG said.
