Britain has signed a deal for the supply of up to 60 million doses of a potential coronavirus vaccine developed by Sanofi and GlaxoSmithKline (GSK).
Financial terms of the agreement were not disclosed.
No vaccine has yet been approved to treat or prevent COVID-19.
The UK could begin vaccinating priority groups, such as frontline health and social workers and those at increased risk from coronavirus, if the treatment proves successful.
The vaccinations would take place as early as the first half of next year, the Department for Business, Energy & Industrial Strategy (BEIS) said.
Human clinical studies of the vaccine will begin in September followed by a phase 3 study in December.
The government has now signed deals for four different types of potential coronavirus vaccines and a total of 250 million doses.
Business Secretary Alok Sharma said: “Our scientists and researchers are racing to find a safe and effective vaccine at a speed and scale never seen before.
“While this progress is truly remarkable, the fact remains that there are no guarantees.
“In the meantime, it is important that we secure early access to a diverse range of promising vaccine candidates, like GSK and Sanofi, to increase our chances of finding one that works so we can protect the public and save lives.”
Sanofi and GSK, which first teamed up in April, have confirmed in a statement that regulatory approval for their vaccine could be won by the first half of 2021 if clinical data was positive.