Government scientist Dame Angela McLean warns against "a wave of infection that spills over into deaths focused in some bits of society”.
Government scientific advisers say lockdown restrictions must be eased gradually – and may have to be imposed again.
Sage committee suggestions to tackle "vaccine hesitancy" and help relieve the "boredom" of self-isolation.
Advisers consider exemption from restrictions after vaccination or infection.
Sage papers on November 4 warned reverting to three tiers system in England would see coronavirus infections rise at "same rate".
Government scientific advisers warn coronavirus restrictions are "undermined by lack of trust in government" among 18-29 year-olds.
Professor John Edmunds tells MPs the "most difficult thing to predict is government behaviour".
Scientist who proposed lockdown also warns pandemic is "far from over".
Sage member Sir Jeremy Farrar says the UK is on a "knife edge" and must get prepared for a second wave later this year.
Ex-scientific adviser to government Neil Ferguson said imposing restrictions a week earlier could have halved coronavirus death toll.