Several elected Europeans point to unjustified delays in vaccine delivery, while the European Union has largely contributed to funding research.
They are awaiting explanations from Commission President Ursula von der Leyen on Wednesday.
Brussels will have to clarify the European strategy for vaccines against Covid-19.
European elected officials have been kept out of the negotiation of contracts with pharmaceutical companies, and today they are calling for accountability.
MEPs will listen to the explanations of Commission President Ursula von der Leyen on Tuesday morning.
They want to understand why Europe seems to be lagging behind and why vaccine deliveries are not arriving as quickly as expected.
"I really expect a frankness from Madame von der Leyen on the why of the failure. Everyone is beyond us when we were among the main providers of funds for the research which led to vaccines", explains the Belgian socialist Marc Tarabella from Europe 1.
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However, no one questions the joint purchase of vaccines.
The Dutch liberal Sophie Int'Veld is rather worried about the lack of pedagogy of the President of the Commission.
"In terms of management, communication, it has not done very well and this has an impact on the confidence of citizens", she argues.
Laboratories do not keep their promises
"All is not perfect", recognizes the MEP Véronique Trillet-Lenoir but for this macronist, if Europe is guilty, it is to have believed the laboratories, especially AstraZeneca which does not keep its promises.
"These are youthful, first-time weaknesses. What was lacking was not so much transparency as the reciprocity of trust in a contract, which AstraZeneca clearly did not follow."
On Tuesday evening, the Commission published a third contract, that of Sanofi / GSK, as a small gesture towards MEPs.