British pharmaceutical firm AstraZeneca has warned that supplies of its coronavirus vaccine to Europe will be "lower than originally anticipated" due to reduced production at a manufacturing site.
The jab it developed with the University of Oxford in England is already being rolled out across the UK, but the European Union has not yet approved its use. It is expected to make a decision by 29 January.
AstraZeneca said in a statement that if EU approval is granted, the "initial volumes will be lower than anticipated", although the start would not be delayed.
The company blamed "reduced yields at a manufacturing site within our European supply chain", without giving details.
It said it would in any case supply the EU with "millions of doses" while ramping up production in February and March.
Stefan De Keersmaecker, European Commission spokesperson for health, said that AstraZeneca had confirmed the change to its delivery schedule at a meeting on Friday and added: "We are working to find out more."
Stella Kyriakides, European Commissioner for health and food safety, said both the commission and member states had expressed "deep dissatisfaction" with the move at a vaccines committee meeting.
"We insisted on a precise delivery schedule on the basis of which member states should be planning their vaccination programs, subject to the granting of a conditional marketing authorisation," she said on Twitter.
.@EU_Commission and Member States expressed deep dissatisfaction with this. We insisted on a precise delivery schedule on the basis of which Member States should be planning their vaccination programs, subject to the granting of a contitional marketing authorisation. /2— Stella Kyriakides (@SKyriakidesEU) January 22, 2021
It was not clear how many doses AstraZeneca had initially been expected to deliver to the 27-country bloc.
The firm said last year it had agreed with the European Commission to supply up to 400 million doses.
The EU has said it has secured contracts for more than two billion doses, more than enough for its total population of 450 million, provided that all the vaccines are approved.
The Oxford-AstraZeneca vaccine is considered key to the global vaccination effort because it is cheaper to produce and can be stored at fridge temperature.
The EU has so far has approved vaccines made by Pfizer-BioNTech and Moderna.
While the coronavirus vaccines have been developed and approved at record-breaking speed, deliveries of the first batches have been smaller than many EU members had hoped.
Pfizer has announced delays in shipments of its vaccine in the next few weeks owing to works at its main processing plant in Belgium.