An unpublished Nordic study prompted Sweden and Denmark on Wednesday to announce a pause on the use of the Moderna vaccine in younger age groups.
The study, which hasn’t been reviewed yet by the European Medicines Agency, raised concern over the risk of myocarditis and pericarditis in this demographic.
JUST IN - Sweden halts vaccinations against #COVID19 with Moderna’s Spikevax for those born 1991 or later, citing side effects including heart muscle inflammation, according to public health authorities (Expressen)
— Disclose.tv (@disclosetv) October 6, 2021
While the risk is small, "the connection is especially clear when it comes to Moderna's vaccine Spikevax, especially after the second dose," the Swedish health agency said in a statement, Reuters reports.
According to the agency, the risk was also more prevalent among young men and boys.
Denmark made the same “precautionary” call, though the Pfizer/BioNTech vaccine was already the primary option for those aged 12-17 in the country.
"In the 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.
Both countries are now recommending the Pfizer jab for minors, which the EMA approved for use in May. Moderna’s Spikevax had been given the green light in July.
In June, the U.S. FDA said it was adding a warning to both Pfizer and Moderna vaccines after a CDC advisory panel said data suggested a "likely association" between the vaccines and rare cases of myocarditis in adolescents and young adults. Despite the warning, doctors and researchers say they still strongly recommend that all Americans 12 and older get vaccinated, noting that the heart problems are uncommon and in most cases very mild.
Two separate vaccine studies subsequently concluded, however, that COVID-19 itself poses a higher risk of symptoms, including heart inflammation, than the vaccines. (CBS)
In the United States, only the Pfizer/BioNTech vaccine is authorized for use in minors.