Finland, as well as Sweden and Denmark, have halted the use of Moderna’s (MRNACOVID vaccine in men aged 30 or younger due to a rare heart inflammation side effect.

In Finland, men born in 1991 and later will receive the Pfizer vaccine, Mike Salminen, director of the Finnish health institute, said in a press conference Thursday, according to Reuters.

Salminen said that men who had already received the Moderna shot could get the Pfizer vaccine as their second dose, Bloomberg reported.

Salminen cited an unpublished Nordic study that included men under the age of 30 from Finland, Sweden, Norway, and Denmark who had received the Moderna Spikevax vaccine, saying that they “had a slightly higher risk than others of developing myocarditis.”

Myocarditis, according to the Mayo Clinic is an “inflammation of the heart muscle” that can reduce the “heart's ability to pump and cause rapid or abnormal heart rhythms.” Symptoms can include chest pain, rapid or abnormal heartbeat, shortness of breath, swelling of the legs, and fatigue.

On Wednesday, both Swedish and Danish health officials announced that they were pausing the use of the Moderna vaccine in all young adults and children, Bloomberg said. The two countries’ officials cited the same study as Finland health authorities.

In Norway, which was also involved in the study, health officials recommended that men under the age of 30 select the Pfizer vaccine for their inoculations, Reuters said.

While the study that the Nordic countries referred to is unpublished, the Finnish institute said it would be published within a couple of weeks and that preliminary data had already been sent to the European Medicines Agency for further review.

According to Reuters, the European Medicines Agency said in July that myocarditis cases could occur in rare instances with the Moderna Spikevax or Pfizer-BioNTech vaccines, especially in young men who had received their second dose of the shot.

However, U.S., EU, and World Health Organization officials have maintained that the benefits of the vaccines continue to outweigh the risks of COVID-19.

A Moderna spokesperson told Reuters regarding the multiple-country pause of the vaccine, “These are typically mild cases and individuals tend to recover within a short time following standard treatment and rest. The risk of myocarditis is substantially increased for those who contract COVID-19, and vaccination is the best way to protect against this.”

As of Thursday premarket hours, shares of Moderna were trading at $305.39, up $2.97, or 0.98%

The US is sending doses of the Moderna Covid-19 vaccine to Ghana Representational image. Photo: POOL / Jacob King