Government scientists have told Downing Street that the vaccine rollout is unlikely to lower the death rate until the end of February.
The vaccines are unlikely to have an impact in January due to the three week delay it takes before they have an effect.
Boris Johnson is under pressure from backbench MPs to announce he is lifting restrictions on March 8.
Mark Harper, Chairman of COVID The recovery group of Conservative MPs said that after that date – three weeks after the deadline to vaccinate the four most vulnerable groups – “what reason could there be to keep the severe restrictions in place for a second of more “.
But if the NHS is still operating at or above capacity, Mr Johnson may be reluctant to follow their demand to remove the severe restrictions at this point.
Some of Mr Johnson’s backbenchers want people under the age of 60 who will still be susceptible to the virus but who will not be vaccinated at that time to have the choice to return to a greater degree of normality.
However, Downing Street will have to determine whether it is worth it given that some of them will always end up in hospital.
Scientists warn it could be March before there is a reduction in pressure on the NHS, which is expected to be under its greatest pressure for a generation over the next few weeks.
In a press conference on Monday, Professor Stephen Powis, medical director of NHS England, said hospital admissions would continue to increase until February.
But Sky News understands government scientists are warning many of them will come from high-risk groups who have yet to receive the vaccine.
They are statistically likely to recover, but only after a long hospital stay. This means that the pressure on the critical capacity of the NHS will continue in March.
It comes as ministers have been warned that there could be more than 250,000 infections per day at certain times this month.
The Office for National Statistics estimates that there were around 1.1 million new infections in the week to January 2.
But at most, according to government scientists, it could add up to more than 250,000 new cases per day.
Government sources told Sky News they do not yet have data to see if the latest lockdown in England, announced by the Prime Minister last Monday, was working.
Initial data showing whether the lockdown in England has worked will only be available from next week at the earliest.
Ministers estimate that it took them two weeks from the day it was introduced to the absolute minimum to see the impact of this lockdown, given that it differs from the first restrictions last March.
The biggest unknown remains whether those who have been vaccinated can no longer transmit the coronavirus.
Pfizer and AstraZeneca vaccines keep people from catching the disease and getting sick, but there is no evidence yet if this will stop the spread.
While all doctors and scientists hope it will, it is still the subject of a major government study.