EU member states plan to buy over 180 million doses of a vaccine designed to combat the Omicron variant.
It's being developed by Pfizer and BioNTech, and is a version of their existing shot.
The pair have said they can have it ready in March.
News of the EU's planned order came late Thursday (December 16) night from European Commission chief Ursula von der Leyen.
A Commission spokesperson said deliveries would start in the second quarter, should the drug be fully approved.
The EU's latest contract with Pfizer and BioNTech allows member states to buy up to 1.8 billion doses through 2023.
About half that amount has already been ordered.
Pfizer says talks about the remaining doses have not yet covered orders for an adapted vaccine.
The European Medicines Agency has so far said there is no conclusive evidence that an Omicron-specific version is necessary.