The Vaccines Taskforce has secured 17 million doses of the Moderna vaccine for the UK – enough for 8.5 million people.
A 28-year-old solicitor from Sheffield was one of the first people to receive the vaccine in England on Tuesday.
The jab has already been rolled out in Wales and Scotland, and the vaccine is expected to be delivered to people in Northern Ireland in the coming weeks.
Here’s what we know about the Moderna vaccine.
How effective is the Moderna vaccine against coronavirus?
The phase three results suggested vaccine efficacy against the disease was 94.1%, and vaccine efficacy against severe Covid-19 was 100%.
More than 30,000 people in the US took part in the trial, from a wide range of age groups and ethnic backgrounds.
Two doses were given 28 days apart so researchers could evaluate safety and any reaction to the vaccine.
The analysis was based on 196 cases, of which 185 cases of Covid-19 were observed in the placebo group versus 11 cases observed in the active vaccine group.
Moderna also released data relating to severe cases.
All 30 severe cases occurred in the placebo group and none in the group which had received the vaccine, known as mRNA-1273.
How many doses of Moderna does the UK have?
The Government has bought 17 million doses – enough to vaccinate about 8.5 million people.
How does the Moderna vaccine work?
The Moderna jab is a messenger RNA (mRNA) vaccine.
Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus’s genetic code.
An mRNA vaccine is injected into the body, where it enters cells and tells them to create antigens.
These antigens are recognised by the immune system and prepare it to fight coronavirus.
No actual virus is needed to create an mRNA vaccine.
This means the rate at which the vaccine can be produced is accelerated.
Is the Moderna vaccine safe?
Moderna said the vaccine was generally well tolerated, with no serious safety concerns identified.
Severe events after the first dose included injection-site pain, and after the second dose included fatigue, myalgia (muscle pain), arthralgia (joint pain), headache, other pain and redness at the injection site.
But these were generally shortlived.
Is the Moderna vaccine effective against variants?
In late January, the company behind the vaccine said it was effective against both the strain first detected in south east England and the mutation which first emerged in South Africa.
Moderna said laboratory tests found no significant impact on antibodies against the UK variant relative to prior variants.
While there was a six-fold reduction in neutralising antibodies produced against the South African variant, the levels remained above those that are expected to be protective, Moderna said.
What stage is the vaccine rollout at?
The NHS in England confirmed that the Moderna jab will be delivered at more than 20 vaccination sites this week, including Reading’s Madejski Stadium and the Sheffield Arena.
More sites will be able to deliver the jab as supply increases.
Almost 40 million vaccines have been delivered across the UK.
This includes more than 32 million first doses and 7.6 million second doses.
The number of first doses being delivered slowed throughout April due to supply constraints.
And the NHS has used the supply it has to offer those at highest risk their second jab.
In England around 94% of people aged 50 and over are likely to have had their first dose of Covid-19 vaccine.
And around 92% of those identified as clinically extremely vulnerable have had their first jab.