Swedish health officials have now decided that a moratorium on giving the Moderna vaccine to anyone under 31 will be extended indefinitely, the U.K. Daily Mail reported. The pause on the Moderna shots had been scheduled to end on Dec. 1.
Finland, Iceland and Denmark have taken similar steps. Norway is encouraging men under 30 not to get the Moderna shot, but is not mandating it.
For months, the Moderna vaccine has been under scrutiny because of data that shows young men who receive it are at increased risk for myocarditis, an inflammation of the heart muscle, and pericarditis, an inflammation of the sac around the heart.
The Daily Mail reported that one U.S. study that has not yet been peer-reviewed concluded that "young males under [age] 20 are up to six times more likely to develop myocarditis after contracting COVID-19 than those who have been vaccinated."
The decision comes as the U.S. Food and Drug Administration is putting Moderna's plans for a shot aimed at the population from age 12 to 17 on hold due to concerns over risks of the ailments, according to The Wall Street Journal.
Dr. Tom Shimabukuro said there is an increased risk of myocarditis and pericarditis with either the Moderna or Pfizer vaccine, in particular after the second dose of the vaccines.
According to the Daily Mail, the data indicated the risk was 13 times greater for those getting the Moderna vaccine than for those who got the Pfizer vaccine.