The European Commission has approved a supply contract with US firm Novavax to buy up to 200 million doses of its potential Covid-19 vaccine, the Commission has said.

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.

Minister for Health, Stephen Donnelly, confirmed Ireland will be participating in this European Commission Advanced Purchase Agreement with Novavax.

He said on Twitter: "It is important that we maintain a broad portfolio of vaccines for the future and Ireland will play a leading role in ensuring vaccines are distributed around the world."

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.

However, 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.

Novavax reached a preliminary deal with the bloc in December, but a final agreement was delayed for months because the US company faced productions problems.

The deal would allow EU states to receive the first Novavax doses from the last quarter of this year, the Commission said.

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Novavax confirmed the deal in a statement and said it was working to complete the submission of vaccine data to the EU drugs regulator in the third quarter of this year, with delivery of initial doses expected to begin after approval.

"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.

WHO urges vaccine makers to keep prices down

The World Health Organization has urged Covid-19 vaccine manufacturers to keep their prices low and affordable, after reports that two producers will raise the cost they are charging the EU.

Pfizer-BioNTech and Moderna are upping the prices for their messenger RNA vaccines because they have adapted them to the new virus variants, according to reports.

The Pfizer vaccine will jump from €15.50 to €19.50 and Moderna from €19 to €21.50, the Financial Times revealed on Sunday, citing the contract concluded with the European Union.

Mariangela Simao, the WHO assistant director general for access to medicines, vaccines and pharmaceuticals, told a press conference on Wednesday: "It's very important that we have companies state policies of affordable prices."

She said both Pfizer and Moderna had increased their manufacturing capacities, diversified their plants and increased production line efficiency.

"In a normal market situation, this would lead to a decreased price, not an increasing price.

"We have a market where the demand is very high in comparison with production.

"WHO urges companies to keep prices down and affordable prices."

Half of the EU population has now been fully vaccinated, according to an AFP tally from official sources.