A jab made by the US firm Novavax could become the fourth vaccine to be approved in the UK after promising data from a late-stage trial emerged.
Nearly 7.5 million people across the UK have received their first dose of a coronavirus vaccine - with the nationwide rollout seen as the country's best hope of bringing the pandemic to an end.
The Pfizer/BioNTech and Oxford/AstraZeneca jabs are already being distributed, while the Moderna vaccine has been given the green light for use.
Watch: UK trials show experimental Novavax coronavirus vaccine is 89.3% effective
But what is so different about the Novavax vaccine - and how many doses has the UK ordered?
How effective is the Novavax vaccine?
Phase 3 trials of the experimental vaccine suggest it is 89.3% effective against COVID-19.
The vaccine candidate was shown to be 95.6% effective against the original strain of coronavirus, and 85.6% effective against the variant first detected in the UK.
The study involved more than 15,000 participants aged 18 to 84, with 27% aged over 65.
Does it work against the South Africa variant?
An early stage study was carried out on 4,400 people in South Africa, including some volunteers with HIV.
Among the HIV-negative volunteers, the vaccine appears to be 60% effective. When immune-compromised volunteers are included, the jab offered 49% protection overall.
Novavax plans to immediately start development on a vaccine specifically targeted to the South African variant.
How does the vaccine work?
The Novavax vaccine differs from those already being used in the UK.
It combines an engineered protein from the virus that causes COVID-19 with a plant-based ingredient to help generate a stronger immune response.
If the body encounters coronavirus in the future, the body is primed to fend it off.
How many doses will be available?
The UK has ordered 60 million vials of the vaccine.
They will be manufactured at the Fujifilm plant in Stockton-on-Tees.
How many doses of the vaccine will each person need?
People will be given two doses of the vaccine, three weeks apart.
How is it stored?
The Novavax vaccine, called NVX-CoV2373, only needs to be stored at fridge temperatures - much like the AstraZeneca and Moderna vaccines.
This means distribution and supply chain management is easier than it is for the Pfizer vaccine, which has to be stored at the much lower temperature of -70C.
How much will it cost the UK government?
The treatment comes at a cost of $16 (Â£11.66) per vaccination.
The jab is therefore more expensive than the AstraZeneca vaccine, but cheaper than both Pfizer and Moderna treatments.