Front line COVID-19 vaccination staff are on standby to go to “maximum capacity” and inoculate twice as many people from next week.
The move to ramp up the rollout comes as supplies of coronavirus doses are due to “substantially increase”.
The rapid expansion will raise hopes the target to vaccinate all adults by the end of July could be brought forward.
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Nadhim Zahawi says the whole country will see a rapid increase in the number of people getting a jab
It comes after Vaccines Minister Nadhim Zahawi told MPs this week he was “expecting tens of millions of doses to come through”, leading to a “rapid increase” in the number of people being injected against COVID-19.
Latest figures show a total of 23,053,716 people in the UK have now received a first dose of coronavirus vaccine.
This is the equivalent of 34.5% of the total UK population, and 43.8% of people aged 18 and over.
Meanwhile, Welsh First Minister Mark Drakeford announced his country had delivered the highest number of jabs so far in a single day at more than 38,000.
NHS England has written to vaccination sites, GPs and pharmacies telling them to prepare to double their vaccination rate from 15 March.
The letter states: “We know that many sites have keenly anticipated an increase in vaccine supply to allow them to operate at maximum capacity.
“The government now expects vaccine supply for new first doses to increase substantially over the weeks of 15, 22 and 29 March.
“Every site should expect to be able to receive, and use swiftly in each of these weeks, around twice the level of vaccine supply previously available with precise details to be confirmed shortly on a site-by-site level.”
As part of the stepped up operation, front line teams have been asked to ensure clinics are booked and patients invited, that reserve lists are in place and that there are extra staff.
A Department of Health and Social Care spokesperson said: “Our health services across the UK are working tirelessly to vaccinate those most at risk and more than 23 million people have already received their first jab.
“The vaccination programme will rapidly expand in the coming weeks as we expect supply to increase substantially and more people will begin receiving their second doses.
“We are confident in our vaccine supplies and remain on track to offer a first vaccine to all adults by 31 July.”
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Speaking to a Commons committee earlier this week, Mr Zahawi said: “In the second half of March you will see a big uplift in supply.
“Up until now supply has been finite.
“We’ve had good volumes but when your supply is finite you have to try and make sure that each region gets enough doses to do the cohort target.
“So when we were focused on [priority groups] one to four by the middle of February, we have to make sure that each region have that vaccine available to them.”
He added: “Now obviously as we see more – and I’m expecting tens of millions of doses to come through – that becomes a little bit easier which allows us, for example, to double the number of pharmacies that will come online for delivery [from 200 to 400].
“The whole country will see a rapid increase in the number of people getting their first dose and getting protected whilst obviously we do second dosing at the same time.”
Mr Zahawi said an estimated 94% of the UK adult population had said they were likely or very likely to take up the coronavirus vaccine.