Large-scale manufacturing of a coronavirus vaccine candidate from French biotech company Valneva has begun in Scotland.
If approved, it would deliver up to 60 million doses to the UK by the end of this year.
Here is everything you need to know about Valneva's coronavirus vaccine candidate.
How does it compare to the Pfizer/BioNTech and Oxford/AstraZeneca vaccines?
Unlike the Pfizer/BioNTech vaccine, which needs to be kept at a temperature of about minus 70C, both the Valneva and Oxford/AstraZeneca jabs conform with the standard cold chain requirements, which is between 2C and 8C.
All three vaccines require a second booster shot to maximise immune response.
Here's how the vaccine rollout has increased since December.
Are there clinical trials in the UK?
The Valneva candidate vaccine is being tested on 150 volunteers at testing sites in Birmingham, Bristol, Newcastle and Southampton.
These tests will show whether the vaccine produces a safe and effective immune response against Covid-19.
If successful, larger tests will be planned for April 2021, with more than 4,000 UK volunteers taking two doses.
These trials will include those aged 18-65 as well as over-65s.
It is the fifth vaccine supported by the National Institute for Health Research (NIHR) to enter clinical trials in the UK, alongside those from Oxford/AstraZeneca, Imperial College London, Novavax and Janssen.
If proven to be a successful candidate, Valneva's vaccine could be available by the end of 2021.
Has the UK Government secured Valneva vaccine doses?
There is an in-principle agreement for 60 million doses, with an option to acquire a further 130 million doses from 2022-2025.
The Government wants to vaccinate the 14million or so people who fall into vulnerable categories by mid-February.
And here is the state of play.
What type of vaccine is this?
Valneva's offering falls into a category of jabs known as inactivated whole virus vaccines.
These vaccines contain viruses whose genetic material has been destroyed by heat, chemicals or radiation so they cannot infect cells and replicate but can still trigger an immune response.
Has this technology been used before?
Yes, this technology is well-established and has been used in seasonal influenza, hepatitis A, polio and rabies vaccines.
The Covid-19 vaccines developed by Chinese companies Sinovac and Sinopharm, and India's Bharat Biotech, which have all been approved for emergency use in their countries, are also inactivated vaccines.
How does the vaccine work?
Sars-Cov-2, the virus that causes Covid-19, is studded with spike proteins which it uses to enter human cells.
While the genetic material virus in the Valneva vaccine candidate has been destroyed, the inactivation process preserves the structure of the spike protein, which helps the body identify the substance as a "foreign invader" and induces an immune response.
So later, when a vaccinated person comes into contact with the virus, the immune system is primed for attack.