A major breakthrough has been announced in the search for a coronavirus vaccine, with the jab from Pfizer found to be more than 90% effective.
The pharmaceutical giant and its partner BioNTech said interim results showed their jab could prevent people catching Covid-19.
Dr Albert Bourla, Pfizer chairman and chief executive, said: "Today is a great day for science and humanity."
The FTSE 100 jumped more than 5.5% on the news, adding £82 (€90.8) billion to the value of its shares in the market's best day since March.
The vaccine has been tested on 43,500 people in six countries and no safety concerns have been raised.
Pfizer and BioNTech plan to apply to the US Food and Drug Administration - the US medicines regulator - by the end of the month for emergency approval to use the vaccine.
The UK Government has secured about 100 million doses of the jab in an agreement with the companies.
About 12 Covid-19 vaccines around the world are currently in the final stages of testing, but Pfizer's is the first to report any results.
Dr 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."
He added: "We will continue to collect further data as the trial continues to enrol, for a final analysis planned when a total of 164 confirmed Covid-19 cases have accrued.
"I would like to thank everyone who has contributed to make this important achievement possible."