Iceland on Friday suspended the use of Moderna’s COVID-19 vaccine because of increased risk of heart inflammation, a rare side effect cited by several other Nordic countries this week.

“As the supply of Pfizer vaccine is sufficient in the territory … the chief epidemiologist has decided not to use the Moderna vaccine in Iceland,” Iceland’s Health Directorate said on its website.

The decision was taken due to “the increased incidence of myocarditis and pericarditis after vaccination with the Moderna vaccine, as well as with vaccination using Pfizer/BioNTech,” the chief epidemiologist said in a statement.

For the past two months, Iceland has been administering an additional dose “almost exclusively” of the Moderna vaccine to Icelanders vaccinated with Janssen, a single-dose serum marketed by another US pharma giant Johnson & Johnson, as well as to elderly and immunocompromised people who received two doses of another vaccine.

Iceland’s campaign to inoculate its 370,000 inhabitants against coronavirus won’t be affected as 88% of the population over 12 years old is already fully vaccinated.

Finland on Thursday also suspended Moderna’s COVID-19 shots to males under age 30, who will be offered the Pfizer/BioNTech vaccine instead. The Finnish Institute for Health and Welfare said it found that young men and boys were at a slightly higher risk of developing myocarditis.

A day before, Sweden suspended the use of Moderna for people under 30, while Denmark said those under 18 won’t be offered the Swiss-made vaccine, and Norway urged those under 30 to get the Pfizer vaccine instead.

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All the countries based their decision on an unpublished study with Sweden’s Public Health Agency saying that it signals “an increased risk of side effects such as inflammation of the heart muscle or the pericardium” — the double-walled sac containing the heart and the roots of the main vessels. It added: “The risk of being affected is very small.”

The preliminary information from the Nordic study has been sent to the European Medicines Agency’s adverse reaction committee to be assessed, according to Associated Press.