CNN  — 

The European Union has authorized the Pfizer/BioNTech Covid-19 vaccine, with the first phase of the bloc’s mass vaccination program to begin later this week.

The move finalizes the recommendation of the European Union drugs regulator, who, just hours before, had granted the vaccine a conditional marketing authorization and paved the way for it to become the first Covid-19 shot distributed in the bloc.

Ursula von der Leyen, President of the European Commission, called it “an important chapter” in the EU’s fight against Covid-19.

“The European Medicines Agency (EMA) assessed this vaccine thoroughly, and it concluded that it is safe and effective against Covid-19,” she said. “As we have promised, this vaccine will be available for all EU countries, at the same time, on the same conditions.”

She said the first batches of the vaccine would be shipped from Pfizer’s manufacturing site in Belgium in the next few days, with vaccinations starting on December 27.

“This is a very good way to end this difficult year, and to finally start turning the page on Covid-19,” von der Leyen said. She added that the EMA would deliver their verdict on Moderna’s vaccine on January 6, potentially giving Europe a second tool with which to battle the pandemic early in the new year.

Harald Enzmann, chair of the EMA’s Committee for Medicinal Products for Human Use (CHMP), earlier said that the agency realized that the speed at which the vaccine has been authorized has been a “cause for concern for many Europeans.” But he stressed that “the data we have analyzed and our assessment of the data have met the standards for robustness and quality.”

Enzmann added that people should continue to keep wearing masks, socially distance and wash their hands, given that vaccine trials haven’t been able to give scientists a clear picture on how vaccines affect transmission.

The authorization comes as a new, rapid-spreading variant of the virus has been detected in countries across Europe, including the UK, Belgium, Denmark, France, Italy, and the Netherlands.

The EMA’s Head of Anti-infectives and Vaccines Marco Cavaleri said on Monday that it was “really too early to say” if the new variant of the virus would compromise the strength of the vaccine, but that “for the time being, we are not worried.”

The UK and the US granted emergency use authorization of the Pfizer/BioNTech vaccine earlier this month, and hundreds of thousands in those countries have since received their first shots.

Equal access

The commission has secured over 2 billion doses of potential vaccines in a move to ensure equitable access across the bloc.

That agreement includes the procurement of 300 million doses of the Pfizer/BioNTech vaccine, which is enough to vaccinate 150 million of the EU’s 448 million citizens.

Ultimately member states will have to buy the vaccines on their own, as the agreement serves as a down-payment.

On Monday, the EMA said that the EU did not know how many doses each member state has in their possession, as that information is held by individual countries only.

And while the commission has also offered guidance on how to deploy them, how each country gets the vaccine to its citizens – and who they choose to prioritize – is up to them.

Most governments have, however, signaled that they are planning to follow EU guidance on prioritizing the elderly, healthcare workers and vulnerable populations first.

Last week, eight countries – Belgium, France, Germany, Italy, the Netherlands, Spain and Luxembourg (as well as Switzerland, which is not in the EU and which authorized the vaccine on Saturday) said they would coordinate their strategies around the rollout. Their joint plan will facilitate a “rapid” sharing of information between each country and will streamline travel guidelines for cross-border workers, who will be prioritized.

Most experts agree that the biggest challenge for the EU will be the actual rollout of the vaccine, given that the Pfizer/BioNTech shot, which uses new mRNA technology, differs significantly from other more traditional vaccines in terms of storage.

It must be stored at around -70C (-94F) and lasts just five days in a refrigerator. Vials of the drug also need to be diluted for injection; once diluted, they must be used within six hours, or thrown out.

The EU vaccine agreement also includes the purchase of up to 160 million doses – enough for 80 million people – from US biotech company Moderna, which could receive EMA authorization as early as January 6.

CNN’s James Frater and Rob Picheta contributed reporting