A Covid-19 vaccine being developed by two leading pharmaceutical companies has been 90% effective at trials.
Pfizer and BioNTech, who are working on the project together, say that, in most cases, preventing infection was achieved seven days on from taking two doses, and 28 days after taking the first.
In a statement, Pfizer boss Albert Bourla said: "The first set of results from our Phase 3 Covid-19 vaccine trial provides the initial evidence of our vaccine's ability to prevent Covid-19.
"We are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis.
"We are reaching this critical milestone in our vaccine development programme at a time when the world needs it most."
Should the vaccine be approved, the companies hope to supply 50 million doses by the end of the year, and 1.3 billion globally in 2021.
The drug, which is currently under Phase 3 of the trial process, has been given to thousands of volunteers, in order to test efficacy and safety.
If it is allowed to move forward, Phase 4 will see it undergo further studies.
The news comes as a leading health expert warned that an outbreak of Covid-19 in minks could halt vaccine development if the mutation proves to be 'dominant'.
Dr Gabriel Scally explained that the new version of the virus may change as it spreads back to people, meaning the race for a way to stop the virus altogether could be slowed down.
A mutated form of coronavirus in the mammals, which are widely bred for their fur, has led to a nationwide cull in Denmark and sent parts of the country into lockdown.
While the mutated strain is not believed to be more dangerous, public health officials fear it could undermine the efficacy of a future vaccine.
