Several EU countries are receiving significantly fewer doses of the Pfizer coronavirus vaccine than expected, after the US firm slowed shipments.
Six nations called the situation "unacceptable" and warned it "decreases the credibility of the vaccination process".
Sweden, Denmark, Finland, Lithuania, Latvia and Estonia urged the EU to apply pressure on Pfizer-BioNTech.
Pfizer said the reduced deliveries were a temporary issue.
In a statement on Friday, the drugmaker said shipments were being affected by changes to its manufacturing processes designed to boost production.
"Although this will temporarily impact shipments in late January to early February, it will provide a significant increase in doses available for patients in late February and March," Pfizer said.
The company said its production upgrades would also have a "short-term impact" on the delivery of vaccines to the UK.
Despite this, the UK government said it still planned to hit its target of vaccinating all priority groups by mid-February - about 15 million people.
The vaccine from Pfizer is not the only candidate available in the UK, with the University of Oxford and AstraZeneca jab also currently being rolled out.
The EU is not wholly reliant on the Pfizer jab either, having approved a vaccine manufactured by US company Moderna for use. Still, the development is expected to slow the pace of vaccination programmes.
The German health ministry called Pfizer's announcement surprising and regrettable, noting that it had committed to binding delivery dates until mid-February.
EU Commission President Ursula von der Leyen said she had been assured by Pfizer's chief executive that all orders guaranteed for delivery in the first quarter of the year would arrive.
Last week, Ms von der Leyen said Pfizer had agreed to supply the EU with 600 million doses this year, double its initial order.
The pledge may do little to soothe European governments battling to subdue a fast-spreading Covid-19 variant first detected in the UK.
https://www.bbc.com/news/world-europe-55666399
