Health Secretary Matt Hancock will lead a Downing Street press conference this evening after the Government said vaccines will be offered to millions of over 70s and the clinically extremely vulnerable from this week.

More than 3.8 million people – including over-80s, care home residents, and NHS and social care staff – have already received their first dose of a Covid-19 vaccine, but from Monday it will be rolled out to the next two priority groups.

The Government said it would remain the priority to vaccinate those in the first two groups, but that sites which have enough supply and capacity to vaccinate more people will be allowed to offer jabs to the next cohorts.

Boris Johnson has pledged to offer vaccinations to the first four priority groups by the middle of next month, while Dominic Raab said on Sunday that all adults would be offered a first dose by September.

Mr Hancock will now lead a Downing Street press conference today, No 10 has said.

It comes as Professor Stephen Powis, national medical director for the NHS in England, said “we are beginning to see” the effects of lockdown measures.

On when the current lockdown measures will have an effect on hospital admissions, he told the PA news agency: “I think we are beginning to see an effect of lockdown measures.

“We know the lockdown measures work, we saw that in April, we saw it in November.

“And we are beginning to see it now and that’s good news because, of course, we have also had this new strain which is more transmissible.

Braintree and Witham Times: A vial of the AstraZenaca covid-19 vaccine. PA PhotoA vial of the AstraZenaca covid-19 vaccine. PA Photo

“So although infection rates are beginning to slow, maybe here in London and a little bit less so in the rest of the country, it will be a number of weeks before we start to see that effect on the number of people in hospitals.”

Professor Powis said the vaccination programme will not reduce pressure on the NHS for “many weeks to come”.

“As the chief executive of the NHS said yesterday, we are in a precarious position at the moment,” he told the PA news agency.

“We have a huge demand on the NHS because of Covid infections since Christmas Eve.

“We have seen 15,000 new people being admitted, so that’s well over 20 hospitals worth of new patients.

“So it’s really important that everybody sticks to those social distancing guidelines that are in place.

“Because the vaccine programme won’t help us in the NHS for many weeks to come.

“So we’re relying at the moment on everybody doing what they’ve done throughout the last year – sticking to the rules, stopping the virus being transmitted. That will reduce deaths and of course it will take pressure off hospitals.”