The reason for the pausing is “signals of an increased risk of side effects such as inflammation of the heart muscle or the pericardium”—the double-walled sac containing the heart and the roots of the main vessels, Sweden’s Public Health Agency said in a statement. “The risk of being affected is very small.”
Anders Tegnell, Sweden’s chief epidemiologist, said they “follow the situation closely and act quickly to ensure that vaccinations against COVID-19 are always as safe as possible and at the same time provide effective protection” against the disease.
In July, the European Medicines Agency recommended authorizing Moderna’s COVID-19 vaccine for children ages 12 to 17, the first time the shot has been authorized for people under 18.
Moderna’s vaccine was given the green light for use in anyone 18 and over across the 27-nation European Union in January.
It has also been licensed in countries including Britain, Canada and the U.S., but so far its use hasn’t been extended to children. To date, the Pfizer/BioNTech vaccine is the only one approved for children under 18 in Europe and North America.
Hundreds of millions of Moderna doses already have been administered to adults.
In a study of more than 3,700 children ages 12 to 17, the vaccine triggered the same signs of immune protection, and no COVID-19 diagnoses arose in the vaccinated group compared with four cases among those given dummy shots.
Sore arms, headache and fatigue were the most common side effects in the young vaccine recipients, the same ones as for adults.
U.S. and European regulators caution, however, that both the Moderna and Pfizer vaccines appear linked to a rare reaction in teenagers and young adults—chest pain and heart inflammation.
The Swedish health authorities said that the heart symptoms “usually go away on their own,” but they must be assessed by a doctor.
The conditions are most common among young men, in connection with, for example, viral infections such as COVID-19. In 2019, approximately 300 people under the age of 30 were treated in hospital with myocarditis.
Data point to an increased incidence also in connection with vaccination against COVID-19, mainly in adolescents and young adults and mainly in boys and men.
New preliminary Nordic analyzes indicate that the connection is especially clear when it comes to Moderna’s vaccine, especially after the second dose, the agency said.
“The increase in risk is seen within four weeks after the vaccination, mainly within the first two weeks,” it said.
The Swedish agency said the vaccine from Pfizer is recommended for these age groups instead. Its decision to suspend the Moderna vaccine is valid until Dec. 1.
In Denmark, people under the age of 18 won’t be offered the Moderna vaccine out of precaution, the Danish Health Authority said Wednesday.
It said that data, collected from four Nordic countries, show that there is a suspicion of an increased risk of heart inflammation when vaccinated with Moderna shots, although the number of cases of heart inflammation remains very low.
The preliminary data from the Nordic study have been sent to the European Medicines Agency’s adverse reaction committee and will now be assessed.
The study was conducted by Denmark’s Statens Serum Institut—a government agency that maps the spread of the coronavirus in the country—the Medical Products Agency in Sweden, the National Institute of Public Health in Norway and the Institute for Health and Welfare (THL) in Finland.
The final results were expected in about a month, the Danish official said.
In Denmark, children and young people ages 12-17 have primarily been invited to receive the COVID-19 vaccine from Pfizer/BioNTech.
“Based on the precautionary principle, we will in future only invite children and young people to receive this vaccine—not least in view of the fact that it is for this vaccine that the largest amount of data from use exists for children and young people, especially from the USA and Israel, said Bolette Soeborg of the government health agency.
Adapted from reporting by the Associated Press