Professor Sir David Spiegelhalter, a member of the Scientific Advisory Group for Emergencies (Sage), warned that intensive care units will still be strained even as deaths drop significantly.
A large number of Tory backbenchers are likely to be among those heaping pressure on the Prime Minister at that point to ease England’s third national lockdown.
Sir David said “the benefits of the vaccine” will begin being seen next month, as he welcomed the “very encouraging news” that the R is estimated to be below 1 across the UK.
That suggests the current restrictions are causing the virus to retreat, and the average infected person is spreading Covid-19 to fewer than one individual.
The University of Cambridge academic told BBC News he is not one for predictions, but added: “The one thing I can be absolutely confident about is that, by this time next month, there is going to be the mother of all arguments.
“Because it’s quite feasible that deaths will have come down considerably, infections should have come down considerably, hospitalisations and ICU will still be under a lot of pressure.
“There will be enormous pressure to loosen things up.
“Loosening it up will inevitably lead to an increase in cases, a resurgence of the pandemic among younger groups, and we can see then that does seep through into hospitalisations.
“So there’s going to be a real battle going on.”
Mr Johnson this week declined to rule out the lockdown lasting into the summer, as he raised concerns about the highly infectious new strain of coronavirus.
The Covid Recovery Group (CRG) of Conservative lockdown-sceptic MPs said ministers “must start easing the restrictions” in March when the top four risk groups should have received some immunity from single jabs.
But the Government’s Scientific Pandemic Influenza Group on Modelling (Spi-M) suggested pubs and restaurants would have to stay shut until May.
It said a wholesale easing of restrictions by the end of April, when all over-50s are expected to have received a vaccine, would be too dangerous.
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