The reproduction number, or R value, of coronavirus has fallen below 1 for the first time since July and is now estimated to be between 0.7 and 0.9 across the UK.
In a sign that lockdown restrictions are having an impact and the epidemic is shrinking, scientists advising the Government gave their most optimistic outlook for the R number since cases fell last summer.
It comes as new data from the Office for National Statistics shows a drop in infections, with around one in 80 people in private households in England having Covid-19 between January 31 and February 6, the equivalent of 695,400 people.
This is down from around one in 65 people for the period January 24 to 30.
The data is based on swab results from people with and without symptoms.
This is down 35% from a peak of 39,236 on January 18, and is the lowest number since December 29.
But while scientists advising the Government believe cases of Covid-19 are dropping at a decent pace across England, they have warned that infection levels remain high.
Prime Minister Boris Johnson is facing calls from Tory sceptics to ease the lockdown once the pressure on the NHS eases and deaths drop.
But scientists argue that case numbers are still too high for a significant loosening of restrictions.
They believe that only by driving case numbers to much lower levels can NHS Test and Trace and surge testing work properly.
With low case numbers, clusters of cases can be identified more easily and new mutations to the virus can be picked up, one Government scientific adviser said.
The current halving time of the virus (the time it takes to the number of new infections to halve in size) is thought to be at around 14 to 17 days.
Scientific advisers believe that if this continues, aided by the rollout of vaccines, then low case numbers can be achieved in the next two to three months.
Meanwhile, NHS England has said people aged 65 to 69 can now have a Covid-19 vaccine in England if GPs have done all they can to reach those at higher risk.
Some parts of England have already begun vaccinating the over-65s with their first dose after they reached everyone in the top four priority groups, including the over-70s and care home residents, who wanted a jab.
NHS England said regions could now move on to people aged 65 and over if every effort has been made to contact and vaccinate those in groups one to four, and if there are supplies.
Once over-65s have been vaccinated, they will be officially followed by all those over 16 with underlying health conditions (group six), then the over-60s, the over-55s and the over-50s.
The Joint Committee on Vaccination and Immunisation (JCVI) is due to recommend which groups should then follow, with pressure for teachers and other frontline workers such as police officers to be on the list.
Some 17% of people aged 60 to 69 and 14% of those aged 50 to 59 in England have received their first vaccine dose, although it is unclear which priority group they fell into.
In Wales, First Minister Mark Drakeford said some over-50s there have already begun to be contacted and offered a vaccination.
Meanwhile, Scotland’s First Minister Nicola Sturgeon has said she expects many in the 65-69 age group to have had their first vaccine by the middle of this month.
And in Northern Ireland, people aged 65-69 have been able to book a Covid-19 vaccine at seven regional centres since the end of January.
However, some GPs have expressed frustration at being told they cannot move on to the next groups.
In other developments, the UK economy shrunk at its fastest rate since the 1920s last year, as the pandemic forced thousands of businesses to remain closed for several months.
GDP dropped by 9.9%.