EU officials have said that Pfizer is yet to deliver to the European Union about 10 million COVID-19 vaccine doses that were due in December.
This leaves the EU about one-third short of the supplies it had expected by now from the Pfizer.
The delay is another blow to the EU, which has also been hit by delays in deliveries from Anglo-Swedish drugmaker AstraZeneca and U.S. company Moderna, and had also faced earlier delays on the Pfizer vaccine.
It also raises questions about the rationale of an EU vaccine export control scheme which was set up in late January to ensure timely deliveries but has not yet been activated, despite the supply shortfalls.
An EU official said that by the middle of last week, Pfizer had delivered to the EU 23 million doses of the COVID-19 vaccine it developed with German firm BioNTech.
That was about 10 million doses less than Pfizer had promised to supplied by mid-February, the official added.
Pfizer declined to comment, saying schedules of its deliveries were confidential. The executive European Commission did not respond to a request for comment on delivery shortfalls.
EU officials have said Pfizer committed to delivering 3.5 million doses a week from the start of January, for a total of 21 million shots by mid-February.
The shortfall would amount to about 30% of the total supplies pledged for the period from December until mid-February.
One EU official said the company had committed to delivering the missing doses by the end of March.
The EU has two contracts with Pfizer for the supply of 600 million vaccine doses.