The move is part of the EU's strategy to diversify its vaccine portfolio after the bloc betted heavily for the coming years on messenger RNA (mRNA) shots produced by Pfizer-BioNTech and Moderna.
"Our new agreement with Novavax expands our vaccine portfolio to include one more protein-based vaccine, a platform showing promise in clinical trials," EU health commissioner Stella Kyriakides said in a statement.
French drugmaker Sanofi, in partnership with British firm GlaxoSmithKline, is also trying to produce a protein-based COVID-19 vaccine and has already signed a supply deal with the EU. But their trials suffered a setback in December, delaying development.
Under the contract, EU states will be able to buy up to 100 million doses of the Novavax vaccine, with an option for 100 million additional doses until 2023, once the shot has been approved by the EU drugs regulator, which is currently reviewing it, the Commission said.
"As new coronavirus variants are spreading in Europe and around the world, this new contract with a company that is already testing its vaccine successfully against these variants is an additional safeguard for the protection of our population," European Commission President Ursula von der Leyen said.
The EU has reserved a total of 2.4 billion doses of the Pfizer-BioNTech vaccine in three different contracts, and has also bought 460 million Moderna shots, clear signs of its preference for mRNA jabs.
It has also booked 405 million doses of the mRNA vaccine developed by CureVac, although the vaccine has so far shown limited efficacy in tests and has not yet been approved by regulators.
The bloc also has supply deals with AstraZeneca and Johnson & Johnson, which both produce viral vector vaccines against COVID-19, but the EU has reduced its reliance on these shots after health concerns and supply problems.
Novavax is the seventh company with which the EU has signed a supply deal for COVID-19 vaccines.