BRUSSELS -- The European Union's executive arm has secured an agreement with Pfizer-BioNTech for an extra 4 million COVID-19 vaccine doses to fight a worrying surge of coronavirus clusters that are prompting the bloc's nations to impose border restrictions.

The European Commission said Wednesday that the deal will help "tackle coronavirus hot spots" and facilitate free border movement. The extra doses, to be delivered in the next two weeks, come in addition to previously planned vaccine deliveries.

"This will help member states in their efforts to keep the spread of new variants under control," European Commission President Ursula von der Leyen said. "Through their targeted use where they are most needed, in particular in border regions, these doses will also help ensure or restore free movement of goods and people. These are key for the functioning of health systems and the single market." 

Despite a slowdown in new infections across the European Union, which has 27 nations and 450 million inhabitants, the Commission said it is worried by the epidemiologic situation in several areas, mainly due to the spread of new variants. It cited Tyrol in Austria, Nice and Moselle in France, Bolzano in Italy and some parts of Bavaria and Saxony in Germany as places where COVID-19 hospitalizations have been on the rise.

The German government approved Wednesday a change to its vaccination rules that allows for areas with particularly high rates of infection to diverge from the usual priority by making shots available to younger and healthier people there too. Vogtland county in Saxony, on the border with the Czech Republic, is planning to offer vaccines to all adults starting Thursday in an effort to stop the coronavirus cases there spreading further into the country.

The European Commission said the new Pfizer-BioNTech doses will be made available for purchase to all member states on a pro-rata basis.

The EU has faced sharp criticism over the slow rollout of vaccinations. While Britain, which left the bloc fully in January, has inoculated 35% of its adults, the EU has only reached 9.5%, according to the latest figures.

Overall, the EU has signed six contracts for more than 2 billion vaccine doses, with Pfizer-BioNTech, Moderna, AstraZeneca, Sanofi-GSK, Johnson & Johnson and CureVac. Only the first three are approved so far and they involve two shots per person. The bloc is also in negotiations with two other vaccine manufacturers.

An expert group at the European Medicines Agency will meet Thursday to decide whether the one-dose coronavirus vaccine made by Johnson & Johnson should be authorized for use, a move that would pave the way for its deployment across the EU.

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Frank Jordans in Berlin contributed to this story.