AstraZeneca is not breaching its contract with the EU. That appears to be propaganda: note that the article doesn't actually state what part of the contract is being breached, and the link in the first paragraph that superficially looks like it would support this claim goes to an article that's not about contracts at all, in fact the word contract doesn't appear anywhere in that article.

The EU accidentally leaked its own contract with AstraZeneca after trying to redact it. It showed that AZ were correct about the wording of the contract and the EU had been lying. There is no real disagreement about that anymore: the EU is on the wrong side of that dispute which is why there's been a lot of posturing but no court cases.

BTW several EU countries have stockpiles of the AZ vaccine they aren't using because their citizens aren't turning up for appointments or volunteering to be vaxxed.

More explicitly, The contract the EU signed gave no priority to the EU over other customers, no exclusivity to EU based on manufacturing location, and no penalty for late delivery.