The health ministry is considering recommending that men under 30 receive Pfizer Inc.’s COVID-19 vaccine rather than the shot developed by Moderna Inc., following an increase in reports of a rare heart disease occurring in younger men after they received the latter vaccine.

The move comes after Sweden halted use of the Moderna shot last week for people born in and after 1991, citing a Nordic study that showed a higher risk of inflammation of the heart muscle, a condition called myocarditis, among young people given the shot. Finland has also paused use of the Moderna jab in men born in 1991 or later.

Concerns have been brewing over myocarditis and pericarditis, the inflammation of the tissue surrounding the heart. For those conditions, there had been 21.60 suspected cases reported per 1 million boys between 10 and 19 who received the Moderna shot by Sept. 12, according to health ministry data published Oct. 1, while the figure was 17.06 for men ages 20 to 29. For those groups who got the Pfizer vaccine, those numbers were 1.87 and 13.08 cases, respectively.