© Andrew MatthewsBoxes of vials of the AstraZeneca Covid vaccine in a fridge at a centre in Bristol (Andrew Matthews/PA)
AstraZeneca is "imminently" scaling up to release two million doses of its vaccine per week in the UK, and may be able to go above that from April, the firm's chief executive has said.
Tom Keith-Roach, president of AstraZeneca UK, said 1.1 million doses of the company's Covid-19 jab developed with Oxford University had been released to the UK to date, but the aim was to reach two million doses per week on or before the middle of February.
He told the Commons Science and Technology Committee: "We are scaling up very rapidly - and this will happen imminently - to releasing two million doses a week.
"We're absolutely on track to do that and therefore deliver tens of millions of doses in the first quarter of the year.
"If we average two million a week through the course of the year, that gets us to the 100 million doses that we're committed to the UK through the course of 2021."
Later, he added: "We are scaling up to two million doses a week imminently and we'd certainly hope to be there on or before the middle of February."
He said the middle of February was a "conservative position" and said the firm had been asked by the UK Vaccines Taskforce "not to share in public forum in detail daily delivery schedules and locations for security reasons.
"As you can imagine it's very sensitive, but I can reassure you that we will scale to two million doses per week very quickly."
Later, he said the firm could not commit to doses above two million per week but it may be they could "increase that somewhat as we move into quarter two".
© Provided by PA MediaThe Oxford AstraZeneca vaccine is one of three approved for use in the UK (PA Graphics)
Mr Keith-Roach also told MPs the "vast majority" of the fill-and-finish packing around the vaccines is done in the UK.
He said the manufacture of the vaccine depends on a complex biological process which cannot be carried out more quickly.
"Drug substance manufacture is a 58 to 60-day process that you cannot speed up - that is a complex biological process of actually growing the adenovirus vector," he said.
Mene Pangalos, executive vice president of biopharmaceuticals research and development at AstraZeneca, added: "You have to grow cells and cells divide at a certain speed, and you can't do any faster than the speed at which the cells divide."
Mr Keith-Roach added: "From drug substance, you have to actually manufacture the drug product.
"That includes filling and finishing, packaging, batch release - that takes a further 28 days.
"If you look in total, you're talking about a three to four-month process.
"Within that you have, as you'd imagine, extensive quality testing on every batch - actually there's more than 60 quality tests that are performed."
Vaccines minister Nadhim Zahawi was accused by Labour MP Graham Stringer of being "phobic" to the numbers and keeping data on vaccine supplies "secret".
Mr Zahawi said "this idea that we are sitting on lots of stock is not true", adding that deliveries of central stocks were unpredictable at the moment.
He told MPs the initial vaccination supply had been "lumpy" but he now had "line of sight" of deliveries to the end of February.
"In any manufacturing process, especially one where you're dealing with a biological compound, a novel vaccine is lumpy at the outset," he said.
"There's no doubt that it was, but getting better. It begins to stabilise and you get much clearer line of sight.
"I now have line of sight of deliveries all the way through until end of February and getting more confidence about March as well.
"We have millions of doses coming through in the weeks and then next month and the month after."
He added that "day by day, what you'll see is greater volumes going out", saying there would be "day-by-day" improvements in the notice given to vaccinators of when supplies will arrive.
And he denied reports that vaccines could not be supplied to the NHS on a Sunday, adding there was a 98.5% accuracy to date in the timing of deliveries.
Earlier, Mr Pangalos said research had begun to examine the mixing of different vaccines to allow greater flexibility in the system.
"(It's) something that we're starting to investigate already, both pre-clinical and clinically."
He also called for people working in the vaccine process to be prioritised for jabs.