The European Commission expects to receive about 200 million doses of the Pfizer/BioNTech Covid-19 vaccine in the second quarter, it said for the first time on Tuesday.
The EU is aiming to vaccinate at least 255 million people, or 70% of its adult population, by the end of the summer but has faced criticism for the slow rollout of its inoculation drive.
Besides supply delays from some drugmakers and hiccups in vaccination plans, the suspension of inoculations using the AstraZeneca vaccine due to potential health issues is also affecting the bloc's campaign.
The EU had not previously said how many doses of the Pfizer/BioNTech vaccine, which is administered in two shots, it would receive in the April-June period under two confidential supply contracts with the drugmakers.
The expected Pfizer second-quarter deliveries will include 10 million doses originally due in the third and fourth quarters of this year, the Commission said.
The announcement does not change the EU's overall forecast for vaccine supplies of 300 million doses in the second quarter from all the drugmakers the bloc has signed contracts with.
"These accelerated 10 million doses will bring the total doses of BioNTech/Pfizer in quarter two up to over 200 million," Commission President Ursula von der Leyen said.
"This is very good news. It gives member states room to manoeuvre and possibly fill gaps in deliveries," she said.
Pfizer confirmed the EU statement regarding its second-quarter supply.
The additional 10 million doses would be moved forward from an option for 100 million doses in a second contract the EU signed with the drugmakers in January, the EU statement said.
In total, the EU has booked 600 million doses from the two companies in the two contracts.
A Commission spokesman told a news conference that the announcement would not lead at this point to a revision of the EU's overall second-quarter delivery forecasts, even though the total announced and expected deliveries was now higher.
The spokesman said delivery schedules could always change so forecasts were not always updated after announcements.
The EU expects to get 55 million vaccine doses from Johnson & Johnson and 35 million from Moderna in the second quarter, according to a delivery schedule published by the Italian government and an internal document on supply forecasts from Germany's health ministry.
AstraZeneca last week announced that it aimed to deliver 70 million doses to the 27-nation bloc in the second quarter, well below its original contractual obligation of 180 million.
In the first three months of the year, the EU expects to receive about 100 million doses from Pfizer, AstraZeneca and Moderna.