Pfizer will temporarily reduce its deliveries to Europe of its vaccine against COVID-19 while it upgrades its production capacity, the company and the Norwegian Institute of Public Health (FHI) said on Friday.

"We received this message today a little before 10am (0900 GMT). We had expected 43,875 vaccines doses from Pfizer in week 3 (next week). Now it appears that we will get 36,075 doses," the FHI said in a statement.

The reduction in deliveries is due to Pfizer limiting output so that it can upgrade production capacity to 2 billion vaccine doses per year from 1.3 billion currently, the FHI said.

"This temporary reduction will affect all European countries," said the FHI. "It is as yet not precisely clear how long time it will take before Pfizer is up to maximum production capacity again.”

Pfizer said it had to make modifications to the process and facility that will require additional regulatory approvals.

"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 in a statement.

Non-EU Norway is getting access to the vaccines obtained by the European bloc thanks to Sweden, an EU member that will buy more than it needs and sell them to Norway.

This coming even as European Commission chief Ursula von der Leyen says Pfizer has guaranteed all promised vaccine doses for the first quarter after six EU states voiced "severe concern" over delays.

(With input from agencies)