Hopes of an end to the Covid-19 pandemic were given a shot in the arm as the NHS begins its rollout of the Oxford / AstraZeneca vaccine.
More than half a million doses of the vaccine - approved by UK regulators on 30 December 2020 - are ready to be administered by the health service.
More than a million people in the UK have already received their first dose of the Pfizer vaccine.
How many doses are currently available to the UK?
There are 530,000 doses of the coronavirus vaccine developed by the University of Oxford and AstraZeneca available in the UK for the start of the rollout on 4 January 2021.
The jabs will initially be administered at a small number of hospitals for surveillance purposes before being rolled out to GP-led services, adding to the 700 vaccination sites in operation.
The UK has acquired 100 million doses of the Oxford jab and 40 million doses of the Pfizer jab through its vaccine taskforce, contributing to the 355 million doses of Covid-19 vaccines overall.
How fast can the NHS administer the vaccine?
The government hopes to administer a combined two million doses of the Oxford and Pfizer vaccines a week by the middle of January, according to Sir John Bell, regius chair of medicine at the University of Oxford.
Speaking to Times Radio, Sir Bell said: “They are then scaling up as we speak, manufacturing capacity so that by the following week we’ll have a flow of vaccines, growing to two million a week by the middle of the month.”
Prime Minister Boris Johnson told viewers of The Andrew Marr Show that “tens of millions” will receive their vaccinations over the next few months.
How long will it take to vaccinate everyone in the UK?
It is the question on everyone’s lips - but the government has as far refused to be drawn on giving a specific date they are aiming for.
Speaking to Andrew Marr on Sunday 3 January 2021, Mr Johnson reaffirmed his prediction that the situation will improve by the spring but warned of tougher restrictions before then.
Sir Jeremy Farrar, director of the Wellcome Trust and a member of Sage, and professor Tim Cook, a consultant in anaesthesia and intensive care medicine at the University of Bristol, have warned there is a long way still to go in the vaccination programme.
"The scale of the vaccination programme should not be underestimated: 1,000 vaccination centres each vaccinating 500 people a day for five days a week, without interruptions of supply or delivery, would take almost a year to provide two doses to the UK population," they wrote in the journal Anaesthesia.
What is the UK’s population?
There are close to 67 million people living in the UK and if everyone were to receive two doses of the vaccine it would require just shy of 134 million doses to be administered.
The government has already changed its tactic in delivering the second dose of the Pfizer jab to 12 weeks after the first, initially from 21 days.
Recipients of the Oxford vaccine will have to wait 12 weeks between the first and second jabs.
Even at two million doses per week, it is still going to take the best part of a year before everyone has received both jabs.
Who will receive a vaccine first?
In order of when people are to be offered the vaccine in the UK:
Care home residents and carers
All those aged 80 years and over and frontline health and social care workers
All those aged 75 years and over
All those aged 70 years and over and clinically extremely vulnerable individuals
All those aged 65 years and over
All individuals aged 16 years to 64 years with underlying health conditions which put them at higher risk of serious disease and mortality
All those aged 60 years and over
All those aged 55 years and over
All those aged 50 years and over
When will I receive the vaccine?
Those curious about finding out when they might receive a Covid jab can get an estimation via a new vaccine calculator online.
The Omni Calculator predicts where you are in the queue to receive a Covid vaccine in the UK, based on the government's priority list.
It asks you to fill out a form stating your age, whether you are a care home resident or worker, if you are pregnant and if you are a health worker.
The tool also needs to know if you were asked to shield during lockdown or are classed as extremely vulnerable, and if you have any underlying health conditions.
By answering all these questions correctly you will receive a more accurate estimation of when you could receive a Covid vaccine.