Some EU countries are receiving much fewer Covid-19 Pfizer vaccine doses than expected, after the US firm slowed shipments.
Six nations called the situation "unacceptable", and warned that it "decreases the credibility of the vaccination process".
Sweden, Denmark, Finland, Lithuania, Latvia and Estonia urged the EU to apply pressure to Pfizer-BioNTech.
Pfizer said the reduced deliveries are a temporary issue.
In a statement yesterday, the drugmaker said shipments were being affected by changes to its manufacturing processes that are 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 EU has also approved a vaccine manufactured by US company Moderna for use, so the bloc is not wholly reliant on the jab developed by Pfizer and its German partner BioNTech. Still, the development is expected to slow the pace of vaccination programmes.
The German health ministry called Pfizer's announcement surprising and regrettable, noting it had committed to binding delivery dates until mid-February.
EU Commission President Ursula von der Leyen said she'd been assured by Pfizer's chief executive that all orders guaranteed for delivery in the first quarter of the year would arrive.
Last week, 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.
About a third of the 27 EU governments reported having "insufficient" vaccine doses, at a meeting this week, Reuters reported, citing a participant.
Lithuania said it would now get only half as many Pfizer vaccine doses as promised, until mid-February.
Belgium said it expected to receive about half the planned doses in January. Canada is also affected, because its vaccine supplies come from a Pfizer factory in Belgium.
Norway, which is not an EU member, said on Friday that Pfizer was temporarily reducing the number of vaccine doses delivered to the country as of next week.
The Norwegian Institute of Public Health said in a statement that it could supplement the loss using "emergency stock"; "The stock we now have will be able to compensate for a reduction in the planned deliveries for a few weeks ahead," it said.
Which other vaccines is the EU buying?
As well as Pfizer-BioNTech, the European Commission has reached agreements with five other pharmaceutical companies to purchase hundreds of millions of vaccines, once they pass clinical trials:
- AstraZeneca: 400 million doses
- Sanofi-GSK: 300 million doses
- Johnson & Johnson: 400 million doses
- CureVac: 405 million doses
- Moderna: 160 million doses
The Commission concluded initial talks with another company, Novavax, for up to 200 million doses.
Elsewhere in the world, Turkey said it had vaccinated half a million people in two days with vaccines developed by China's Sinovac Biotech.
The figures suggest Turkey vaccinated more people on the first day of its rollout than France did in almost three weeks.
In the US, President-elect Joe Biden unveiled a US$1.9tn (NZ$2.66tn) stimulus plan for the coronavirus-sapped US economy on Thursday night.
If passed by Congress, it would include $1tn for households, with direct payments of $1,400 (almost NZ$2000) to all Americans.
-BBC