Brussels and Pfizer/BioNTech on Thursday signed a deal for the European Union to receive an additional 1.8 billion doses of the COVID-19 vaccine by 2023.
The contract also enables the 27-country bloc to purchase an additional 900 million doses, the Commission said in a statement.
It also stipulates that all the doses must be manufactured in the European Union and that their essential components must also be sourced from the bloc.
"With our signature, the new contract is now in force, which is good news for our long-term fight to protect European citizens against the virus and its variants," Commission President Ursula von der Leyen said.
"Potential contract with other manufacturers will follow the same model, to the benefit of all," she added.
The EU has so far received over 201 million doses of the vaccines — 150 million of which are Pfizer/BioNTech which requires two doses to be fully effective.
This latest contract adds to the 2.3 billion doses Brussels has ordered from various pharmaceutical companies. So far, only four jabs have been approved by the European regulator: Pfizer/BioNTech, AstraZeneca, Moderna and Johnson & Johnson.
Only the one developed by Johnson & Johnson requires a single dose.
But the emergence of variants, believed to be more transmissible and resistant to treatment, has raised concerns the vaccines already distributed may not protect against new strains.
The European Medicines Agency has however said it is "pretty confident" that mRNA vaccines — which include Pfizer/BioNtech and Moderna — are effective against a new Indian variant.
The B.1.617 variant, which was first discovered in Indian in October, has since spread to more than 40 countries. Experts believe it is partly to blame for a surge in infections and deaths in India in recent weeks.
Pfizer CEO Albert Bourla, as well as authorities in several countries, have meanwhile suggested that a third booster dose may be necessary within 12 months of the second dose.
In a statement on Thursday, he said that "Ongoing vaccination beyond 2021 is critical as COVID-19 continues to spread rapidly throughout Europe and the globe."
"More than a year later, we continue to learn about COVID-19 and are working to determine if, similar to seasonal influenza, annual vaccination may provide the most enduring protection," he went on.
The Commission also said that the new contract reinforces the "possibility for member states to resell or donate doses to countries in need outside the EU or through the COVAX Facility."
Rich countries have so far bought the bulk of COVID-19 vaccines. The World Health Organisation and an independent panel of experts have urged them to donate more doses, more quickly.