Lots of comments are complaining about how EU "paid less" for the vaccine than country XYZ, but actually EU funded AstraZeneca with hundreds of millions of euros to develop the vaccine in the first place.
In any case unless AZ, EU etc. are able to come to reasonable agreement I think this might eventually lead to EU simply breaking the patent and then anyone can make the vaccine. That would be extremely hardcore measure to use, but in current situation, definitely possible.