Officials in Sweden and Denmark have paused use of the Moderna COVID-19 vaccine in younger age groups due to concerns about the shots causing rare heart inflammation.
The two Nordic nations - separated by only a dozen miles of the Kattegat sea area - announced the decision on Wednesday.
In Sweden, the Moderna jab will no longer be available to any one born after 1990, or those aged 30 and younger.
Denmark has restricted access to the vaccine to anyone under the age of 18.
Myocarditis and pericarditis, both types of inflammation of the heart, are known as side effects of the Covid vaccines, and the Centers for Disease Control and Prevention (CDC) even warns that the condition may develop in young males after vaccination.
Heart inflammation is also a symptom of many viral infections like COVID-19, though, and the likelihood of developing the inflammation after infection is much higher than it is after vaccination.
Use of the Moderna vaccine has been paused in Sweden for people born after 1990 and in Denmark for people younger than 18 (file photo)
The Moderna vaccine has been tied to cases of heart inflammation, particularly in young people, leading to officials in the Nordic country putting a pause on its use in some populations. Pictured: A woman in Ishoej, Denmark, receives a dose of a COVID-19 vaccine on September 11
The Swedish health agency said it would pause using the shot for people born in 1991 and later as data pointed to an increase of myocarditis and pericarditis among youths and young adults who had been vaccinated.
The pause will last until December 1.
Those conditions involve an inflammation of the heart or its lining.
'The connection is especially clear when it comes to Moderna's vaccine Spikevax, especially after the second dose,' the health agency said, adding the risk