STOCKHOLM, October 6 (Reuters) – Sweden and Denmark on Wednesday announced they were suspending the use of Moderna’s COVID-19 vaccine (MRNA.O) for younger age groups after reports reported possible rare cardiovascular side effects.

The Swedish health agency said it would discontinue use of the vaccine for people born in 1991 and later because data indicated an increase in myocarditis and pericarditis in young people and young adults who were vaccinated. These conditions involve inflammation of the heart or its lining.

“The link is particularly clear when it comes to Moderna’s Spikevax vaccine, especially after the second dose,” the health agency said, adding that the risk of being affected was very low.

Moderna shares fell 4.9%, or $ 16.08, to $ 316.11 in afternoon trading.

A Moderna spokesperson said in an email that the company was aware of decisions by Danish and Swedish regulators to suspend use of its vaccine in young people due to the rare risk of myocarditis and / or pericarditis.

“These are usually mild cases and individuals tend to recover quickly after standard treatment and rest. The risk of myocarditis is significantly increased for those who contract COVID-19, and vaccination is the best way to avoid it. protect.”

Young men under the age of 20 are up to six times more likely to develop myocarditis after contracting COVID-19, according to a US study that has not yet been peer reviewed. who have been vaccinated.

Denmark said that although it was using the Pfizer / BioNTech vaccine as the primary option for people aged 12 to 17, it had decided to suspend administration of the Moderna vaccine to people under the age of 18 according to a ” precautionary principle”.

“In preliminary data… there is a suspicion of an increased risk of heart inflammation, when vaccinated with Moderna,” the Danish health authority said in a statement.

He referred to data from an as yet unpublished Nordic study, which would now be sent to the European Medicines Agency (EMA) for further assessment. Final data was expected within a month, he added.

Sweden and Denmark said they are now recommending the Comirnaty vaccine, from Pfizer / BioNTech (PFE.N), instead.

The Danish health authority said it made the decision even though “heart inflammation is an extremely rare side effect which often has a mild course and goes away on its own.”

The EMA’s safety committee concluded in July that inflammatory heart disease can occur in very rare cases after vaccination with Comirnaty or Spikevax, more often in younger men after the second dose. Read more

The benefits of injections based on the so-called mRNA technology used by both Moderna and Pfizer-BioNTech to prevent COVID-19 continue to outweigh the risks, US, EU regulators have said and the World Health Organization.

The data suggests that reported cases of rare heart inflammation are relatively higher after Moderna’s vaccine compared to Pfizer / BioNTech injections, Canadian health officials said last week. Read more

Although both vaccines are based on mRNA technology, the Pfizer vaccine contains 30 micrograms of vaccine per dose, compared to 100 micrograms in the Moderna vaccine.

Data from one of the two US vaccine safety surveillance databases also suggested that Moderna’s vaccine may carry a higher risk of myocarditis in young people.

The vaccine is not approved for people under the age of 18 in the United States.

Norway already recommends the Cominarty vaccine to minors and said on Wednesday it was repeating it.

“Men under 30 should also consider choosing Cominarty when getting vaccinated,” Geir Bukholm, infection control manager at the Norwegian Institute of Public Health, said in a statement.

A Finnish health official said Finland expected to release a decision on Thursday.

The EMA approved the use of Comirnaty in May, while Spikevax was given the green light for children over 12 in July. Read more

Reporting by Johan Ahlander in Stockholm and Stine Jacobsen in Copenhagen; Additional reporting by Gwladys Fouché in Oslo, Julie Steenhuysen in Chicago, Michael Erman in New York; Editing by Kirsten Donovan, Alex Richardson and Alison Williams

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