At least 15 million people in the UK have received at least one dose of a coronavirus vaccine - part of the biggest inoculation programme the country has ever launched.

In a race against a faster-spreading variant of the virus, ministers have pinned their hopes of ending a third national lockdown on protecting the most vulnerable groups by spring.

But there are huge challenges, not least the unprecedented scale and supply demands, but also the need for rigorous safety checks and deep-freeze storage.

The government had aimed to offer vaccines to 15 million people - those aged 70 and over, care home residents, healthcare workers and people required to shield - by mid-February and millions more people aged 50 and over and other priority groups by spring.

These groups account for 88% of deaths so far.

The UK has now delivered 15 million vaccinations and ministers say the UK is on track to meet its pledge of offering a vaccine to everyone in the top four priority groups by Monday.

A small number of the 15 million to receive a jab will have been outside these priority groups.

The number of first doses administered each day has been steadily climbing since December - with a current seven-day average of more than 435,000.

The campaign to reach as many people as quickly as possible was boosted by a shift in policy in early January - to prioritise the first dose of a vaccine, with a second dose up to 12 weeks later, a bigger gap than originally planned.

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Overall, more than 15 million people have now received a first dose in the UK. More than 530,000 of those have received a second dose.

This progress means the UK continues to be among the countries with the highest vaccination rates globally.

The speedy rollout of the vaccine to all vulnerable people is seen as critical to reducing the pandemic's death toll and relieving pressure on the NHS.

From Monday, the vaccine rollout is being expanded to include over-65s and those deemed clinically vulnerable. The rest of the over-50s will follow.

From spring, the government plans to begin vaccinating the rest of the adult population, another 21 million people. Teachers, transport workers, supermarket workers and the military could be prioritised.

Within the UK, there has been some regional variation in the vaccination rollout - in particular between the nations.

All English regions except London have now jabbed more than 80% of people aged 70 or above with their first dose - a total of 6.5 million people, according to weekly data released on Thursday.

A further 365,000 people in the same age range have received their first dose in Wales (73%) and 473,000 in Scotland (64%) - as of 7 February.

The Northern Ireland Health Department says that 61% of people aged 70 and over received their first dose in the same time frame.

There are also disparities between ethnic groups and poorer and wealthier areas.

Analysis of NHS records by the OpenSAFELY group - a collaboration between Oxford University and the London School of Hygiene and Tropical Medicine - shows that black people were the least likely to have received a vaccine among those aged 80 and over, while white people were the most likely.

The study was based on more than 20 million patient records in England and covers people not living in care homes. Areas of London are under-represented in the data.

In addition, only 73% of those aged 80 and over in the poorest areas had been given the vaccine by 27 January compared with 85% in the most affluent areas.

The UK is currently receiving doses of two vaccines approved by the medicine regulator.

The Pfizer-BioNTech jab - the first to be given the green light in December - is being imported from Puurs, Belgium.

A second vaccine, from Oxford University and AstraZeneca, is being made in Britain by two biotech companies: Oxford BioMedica, based in Oxford; and Cobra Biologics, based at Keele Science Park, Staffs.

Another company, Wockhardt, based in Wrexham, fills the vials and packages them for use.

Supplies of a third vaccine to be approved, made by US company Moderna, will come from Switzerland or Spain but are not expected to be available until spring.

The UK is also lined up to receive at least three other vaccines if they are approved for use.

A jab manufactured by US firm Novavax will be made in Stockton-on-Tees in north-east England, while another by French company Valneva will be made in Livingston, West Lothian, Scotland.

The third, by Belgian firm Janssen, owned by Johnson & Johnson, should also be available later this year.

People will be vaccinated in three main ways, at:

The government has urged the public to "play their part" in supporting "the largest vaccination programme in British history", including helping people attend their appointments.

In England, more than 1,500 sites, including GPs' surgeries, community pharmacies and hospital hubs, are offering vaccination services.

They also include 90 major vaccine sites which have been set up in larger premises, such as sports centres, racecourses and showgrounds, which are capable of giving jabs to thousands of people a week.

In Wales, the vaccine is being distributed at GP practices and by mobile units. And they hope to have 35 mass vaccination centres up and running in the coming weeks.

In Scotland, as well as GPs surgeries, pharmacies and hospital hubs, there will also be a number of larger vaccination sites, including 16 in the Greater Glasgow and Clyde area.

The UK has ordered 407 million doses of seven of the most promising vaccines - three of which have so far been approved for use.

Among them are 100 million doses of the Oxford vaccine - enough to inoculate 50 million people.

This, when combined with the 40 million ordered Pfizer jabs, will cover the entire population, Health Secretary Matt Hancock has said.

The UK also has significant orders of the Moderna vaccine, which was approved in January.

But having vaccines on order is not the same as having them ready to go.

There have been a number of challenges in what is called the vaccine "supply chain" - the logistics of how the jab gets from manufacturers to people.

Getting enough supplies in the first place, checking those supplies are up to scratch and transporting vaccines according to their requirements have all thrown up difficulties.

Design by Lilly Huynh, Irene de la Torre Arenas and Sana Jasemi. Data journalism by Wesley Stephenson, Christine Jeavans and Daniel Dunford.

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