The EU has struck a deal for up to 160 million doses of the Moderna vaccine, which could be finalised soon, the European Commission's president said on Tuesday.
Ursula von der Leyen said the bloc had "one of most comprehensive portfolios of COVID viruses in the world", with the new jab taking its potential stock to nearly 2 billion.
US biotechnology company Moderna announced that its vaccine appeared to be 94.5% effective after just five COVID-19 cases were reported in the group that received two doses of the mRNA vaccine.
This efficacy rate is likely to go down as the trial continues, experts say, though many have hailed the results as encouraging.
The EU has concluded multiple contracts for vaccines, including one with CureVac, a European company that is also working on a vaccine candidate.
Von der Leyen said that the EU had agreed to buy up to 405 million doses of the vaccine if successful. The bloc concluded an agreement with Pfizer and BioNTech after news of the efficacy of their vaccine as well.
The Pfizer agreement was for "a supply of 200 million doses and an option to request additional 100 million doses" the pharmaceutical company said in a statement.
Commission spokesman Stefan De Keersmaecker said that the EU wanted to develop a "diversified and broad portfolio of different vaccine candidates" since it is unknown which vaccine candidate will be effective, safe and available.
That is why they have multiple agreements with vaccine developers, the spokesman said.
He added that there is a risk of that "some of the investments will not come to successful vaccines" which is why they reduce the risk by investing in multiple providers.
Any vaccine would need to be reviewed and authorised by the European Medicines Agency before distribution.