Finland's institute for health and welfare has said that the country will pause the use of Moderna's (Nasdaq:MRNA) COVID-19 vaccine for men born in 1991 and later due to reports of a rare cardiovascular side effect, Reuters news agency reported on Thursday.

The director of the health institute, Mika Salminen, stated: "A Nordic study involving Finland, Sweden, Norway and Denmark found that men under the age of 30 who received Moderna Spikevax had a slightly higher risk than others of developing myocarditis."

This condition, an inflammation of the heart muscle, usually heals on its own in a few days. However, as a precaution Finland would only give Pfizer's (NYSE:PFE) vaccine to boys and young men, Salminen said.

Sweden and Denmark have suspended the use of the Moderna vaccine for all young adults and children.