STOCKHOLM — Sweden and Denmark decided to halt vaccinations with Moderna Inc.’s COVID-19 shot for younger people because of potential side effects.
The Swedish health authority Wednesday cited new data on the increased risk of heart inflammation as a reason for the pause for those age 30 and under. Denmark will stop giving the shot to those younger than 18.
Moderna shares fell as much as 5.3% in New York trading.
“We are monitoring the situation closely and are acting rapidly to ensure that COVID-19 vaccinations are constantly as safe as possible, while also providing protection,” said Anders Tegnell, Sweden’s chief epidemiologist.
The two countries recommended Pfizer Inc.’s and BioNTech SE’s rival vaccine as a replacement. Both vaccinations use messenger RNA technology to prompt an immune reaction.
Sweden’s public health watchdog said a new preliminary analysis from the Nordic region indicates that the connection between vaccination and heart inflammation is clearest with the Moderna shot, especially after the second dose. The higher risk comes within four weeks of vaccination, and usually in the first two weeks, it said.
In an interview, Moderna Chief Executive Officer Stephane Bancel said that larger data sets including real world data from the United States indicate that the risk of myocarditis is similar between the two vaccines. Also, he said the risk of contracting myocarditis from COVID-19 is much greater than the chances of coming down with the heart condition after getting the vaccine.
Those who have been vaccinated recently with a first or second dose of the Moderna vaccine shouldn’t worry, Tegnell said, as the risk is very small. Denmark’s National Board of Health indicated it hasn’t seen any differences in side effects between the two vaccines.
The Norwegian Institute of Public Health cited new data from Ontario, Canada, as well as from Norway, Sweden and other countries in recommending that men under 30 consider choosing the Pfizer jab.
On Monday, the European Medicines Agency authorized the use of an extra dose of Moderna’s shot for those with a severely weakened immune system.
Last week, Slovenia temporarily halted another type of vaccine made by Johnson & Johnson after the death of a young woman who had received it. Earlier this year, a number of countries placed age restrictions on AstraZeneca Plc’s shot due to links with other potential side effects.
The Astra and J&J vaccines use technology called a viral vector that’s different from the mRNA shots.
