It been taken to a central hub at an undisclosed location in unmarked lorries before it is moved to hospitals and vaccination centres across the country.
The UK has ordered 40 million doses of the vaccine, which is enough to vaccinate 20 million people.
Its arrival on Thursday spells joy for the families of elderly people, NHS and care home staff and vulnerable groups, who will be among the first to receive it.
Coronavirus: The 53 vaccine delivery hubs in the UK
The development came on the same day the UK became the first country in Europe to surpass 60,000 coronavirus deaths.
A refrigerated truck was earlier seen leaving the Pfizer manufacturing plant in Puurs, Belgium, on Thursday morning.
Officials at Pfizer and in Whitehall were keeping tight-lipped because of security concerns and the vaccine travelled in unmarked lorries.
The international community has raised eyebrows over how quickly the UK approved a Covid-19 vaccine.
America’s top infectious disease expert Anthony Fauci questioned the level of scrutiny.
Dr Fauci, the director of the US National Institute of Allergy and Infectious Diseases, claimed American regulators “would do a more thorough job” of assessing the vaccine developed by Pfizer/BioNTech.
The World Health Organisation (WHO) offered a toned down response to the Medicines and Healthcare products Regulatory Agency’s (MHRA) decision, simply stating the approval had been “acknowledged”.
Dr Fauci told CBS News that Britain “kind of ran around the corner of the marathon and joined it in the last mile”. He added: “They really rushed through that approval.”
Dr Fauci said: “The FDA, the United States of America Food and Drug Administration, is the gold standard of regulation.
“They are doing it in a careful way, appropriately.”
In response to the comments, the MHRA said in a statement: “We have rigorously assessed the data in the shortest time possible, without compromising the thoroughness of our review.
“Covid-19 vaccines, including this one, are being developed in a co-ordinated in a way that allows some stages of this process to happen in parallel to condense the time needed, but it does not mean steps and the expected standards of safety, quality and effectiveness have been bypassed.”
The European regulator has criticised the approval of the vaccine using emergency powers, insisting that its own, slower approach is more appropriate.
Despite this criticism, a Cabinet minister declared the UK is getting a coronavirus vaccine first because it is a “much better country” than France, Belgium and the US.
Education Secretary Gavin Williamson praised the work done by the medical regulator to approve the Pfizer/BioNTech vaccine for use.
Jonathan Van-Tam ‘hopeful vaccines are going to make big impact’
Issues surrounding storage temperature and how many times it can be transported have prompted the Prime Minister to warn of “immense logistical challenges” in the Pfizer rollout.
Experts have said that people in care homes might face a delay in receiving immunisation from the disease.
However, the Scottish Government has said care homes in the country will get the jab from December 14, raising questions for care home residents in other parts of the UK.
The Medicines and Healthcare products Regulatory Agency (MHRA) said on Wednesday that batches could be made smaller in a document outlining conditions of authorisation.
On Wednesday evening at a Downing Street press conference, the chief executive of NHS England Sir Simon Stevens said the vaccine would not reach care homes until approval that it could be safely divided.
When asked for comment, NHS England would not commit to a date to roll the vaccine out in English care homes.
The MHRA document said “further packing down” of batches to aid deployment could occur at 2C to 8C within 120 hours of leaving cold storage.
Scotland’s Health Secretary Jeane Freeman said talks over lunchtime on Thursday had confirmed that the vaccine could be transported in an unfrozen state for up to 12 hours and could also be broken down into smaller packs in “certain conditions”.