STOCKHOLM — Swedish health authorities decided Wednesday to suspend the use of Moderna’s COVID-19 vaccine for those born in 1991 and later, saying it was a precautionary measure related to heart inflammation.

The Swedish Public Health Agency says the reason is “signals of an increased risk of side effects such as inflammation of the heart muscle or the pericardium. ” That’s the double-walled sac containing the heart and the roots of the main vessels. The agency added the risk is very small.

U.S. and European regulators have cautioned about Moderna and Pfizer vaccines and an extremely rare reaction in teens and young adults of chest pain and heart inflammation. The Swedish agency says the vaccine from Pfizer is recommended for these age groups instead. Its decision to suspend is valid until Dec. 1.

In Denmark, people under 18 won’t be offered the Moderna vaccine out of precaution, according to the Danish Health Authority on Wednesday. The agency says data, collected from four Nordic countries, show there is a suspicion of an increased risk of heart inflammation when vaccinated with Moderna. It adds the number of cases of heart inflammation remains very low.