This comes as AstraZeneca warned that EU countries will receive less of the vaccine than anticipated in the coming months.
The European Union will make companies respect vaccine deals, according to EU President Charles Michel.
Michel said that he would ensure that contracts would be respected "using legal means".
Speaking on Europe 1 Radio, he said: "We plan to make the pharmaceutical companies respect the contracts they have signed by using the legal means at our disposal."
AstraZeneca warned on Friday that supplies of its coronavirus vaccine to Europe will be "lower than originally anticipated" due to reduced production at a manufacturing site.
AstraZeneca said in a statement that if EU approval is granted, the "initial volumes will be lower than anticipated".
An Taoiseach Micheál Martin also said that vaccinations for people over the age of 70 may be delayed as a result. He said that the situation has put us in a "real problem".
Michel also discussed whether Europe will be able to vaccinate 70% of its population by September.
He said: "There are difficulties in the production lines in the coming weeks and that will make the process more complex but if we manage to mobilize the production lines, we may be able to succeed. It's going to be difficult."
Ireland's Minister for Health has said that every adult in Ireland will have been offered a Covid vaccine by September.
