European Commission President Ursula von der Leyen has said the EU may restrict vaccine exports to countries outside the bloc.
The 27-nation region has been facing a shortage of coronavirus vaccines for some time.
President von der Leyen spoke as six EU countries complained about reduced deliveries that are hampering the bloc's troubled inoculation programme.
With the EU facing a third wave of the coronavirus pandemic and less than a tenth of its population vaccinated, President von der Leyen accused AstraZeneca of having "underproduced and underdelivered".
She warned she was "ready to use whatever tool we need" to ensure "Europe gets its fair share".
"We are in the crisis of the century," she said.
"If this situation does not change, we will have to reflect on how to make exports to vaccine-producing countries, dependent on their level of openness.
"We will reflect on whether exports to countries who have higher vaccination rates than us are still proportionate."
The EU has been exporting vaccines in support of global cooperation.
But open roads run in both directions.
If needed we’ll reflect on how to adjust our exports based on reciprocity and, in the case of countries with higher vaccination rates than us, proportionality.
— Ursula von der Leyen (@vonderleyen) March 17, 2021
President von der Leyen said the EU has granted 314 requests for vaccine exports and has only refused one since authorisation was introduced on February 1st.
She said the flow of vaccines was smooth with the United States, but voiced frustration over lack of deliveries of the AstraZeneca vaccine from Britain.
"We are still waiting for doses to come from the UK," she said.
Meanwhile, as of Sunday, 617,050 doses of the COVID-19 vaccine have been administered in Ireland.
To date, more than 750,000 doses of the inoculation have been delivered here.
Of those, more than 200,000 are from AstraZeneca.
At this time, WHO considers that the benefits of the AstraZeneca vaccine outweigh its risks and recommends that vaccinations continue.
Full statement on AstraZeneca #COVID19 vaccine safety signals:
👉 https://t.co/9J6MtxXWK8 pic.twitter.com/fWGzqbjMuE
— World Health Organization (WHO) (@WHO) March 17, 2021
In a statement today, the World Health Organisation recommended that vaccines made by AstraZeneca continue to be administered, saying the benefits outweigh the risks.
Ireland is one of a dozen countries that have paused the rollout because of reports of blood clotting.
The European Medicines Agency is continuing to assess the safety of the vaccine before making a final decision tomorrow.