The EU is demanding that AstraZeneca deliver the COVID-19 vaccines that it says were missed in the first quarter.
A total of 90m doses of the jab were not delivered by the end of March, the European Commission said on Tuesday.
Brussels said AstraZeneca could face financial penalties if the remaining doses of the 120 million promised are not delivered to EU member states by the end of June.
It is the first time the European Commission has specified its demands during its legal proceedings against the British-Swedish pharmaceutical giant.
"The company has not fulfilled its contractual obligations," an EU spokesperson said, announcing this second legal action.
Reports suggest AstraZeneca is only planning to deliver 70 million out of the 180 million earmarked for the EU by the end of this second quarter.
Significant delays in vaccine supply led the European executive to take the company to court in Brussels in April to force it to respect its commitments.
Euronews has reached out to AstraZeneca for comment.