BRUSSELS, Jan. 16 (CNA) - European governments said the credibility of their vaccination programmes was at risk on Friday (Jan 15) after US pharmaceutical firm Pfizer announced a temporary slowdown of deliveries of its COVID-19 vaccines.

Shots developed by Pfizer with its German partner BioNTech began being delivered in the EU at the end of December, but around nine of the 27 EU governments complained of "insufficient" doses at a meeting this week, a participant said.

Pfizer initially said deliveries were proceeding on schedule, but then on Friday announced there would be a temporary impact on shipments in late January to early February caused by changes to manufacturing processes to boost output.

"This situation is unacceptable," the health and social affairs ministers of six EU states said in a letter to the EU commission about the Pfizer delays.

"Not only does it impact the planned vaccination schedules, it also decreases the credibility of the vaccination process," the ministers, from Sweden, Denmark, Finland, Lithuania, Latvia and Estonia said.

Germany, Europe's largest purchaser of the Pfizer vaccine, called the decision surprising and regrettable, while Canada said it was also affected, because its supplies come from a Pfizer factory in Belgium.

Norway and Lithuania had earlier said the company was reducing supplies across Europe. "What we want is for Pfizer-BioNTech to restore their deliveries to the agreed schedule," Lithuanian health minister Arunas Dulkys told Reuters.

The President of the European Commission Ursula von der Leyen said Pfizer had reassured her that deliveries planned to the EU in the first quarter would not be delayed.