At least 23 people who received the COVID-19 vaccine developed by U.S. firm Pfizer and Germany's BioNTech have died in Norway, with 13 of the fatalities linked to the vaccine's side effects, authorities said Thursday.

All 13 individuals were above the age of 80, according to the Norwegian Medicines Agency.

It noted that the Pfizer-BioNTech vaccine's common side effects, such as fever and nausea, could have contributed to the death of some elderly recipients of the shot.

Along with the 13 deaths, nine cases of serious side effects and seven instances of less serious side effects have been recorded, the agency's medical director, Steinar Madsen, told national broadcaster NRK.

Norway launched its vaccination campaign last month, right after the Pfizer-BioNTech vaccine was approved by the European Medicines Agency (EMA).

Nearly 33,000 people have received a dose in the country, according to data by U.K.-based tracker OurWorldInData.

The latest figures show Norway's virus caseload currently stands at 57,736, including 511 fatalities.