Update (November 10): Germany has joined other countries in recommending Pfizer’s COVID-19 vaccine for people under 30, as research from the Paul Ehrlich Institute, Germany’s vaccine authority, found rates of heart inflammation were higher after the Moderna vaccine than after Pfizer/BioNTech’s, reports Reuters.

Update (November 9): The French health advisory body Haute Autorite De Sante announced yesterday it recommends Pfizer’s Comirnaty vaccine for those under 30 years of age as a study found the risk for heart inflammation in this population is 5 times lower than for Moderna’s Spikevax vaccine, Reuters reports.

Update (October 15, 2021):  According to Reuters, some countries are only administering one dose of the Pfizer/BioNTech vaccine in children and teenagers out of concern over possible rare cardiovascular side effects, which are more common after the second shot than the first. These include Norway, South Africa, and the United Kingdom.

Update (October 11): According to Reuters, the Danish Health Agency has retracted its statement about pausing the Moderna vaccine for those under 18 years old, and is in fact still using both Moderna’s and Pfizer’s vaccines in this age group.

Update (October 8, 2021): Finland’s health agency announced yesterday that it is suspending use of Moderna’s Spikevax shot in males under 30 years of age, who will be offered the Pfizer/BioNTech vaccine instead, the Associated Press reports.

The Danish Health Agency is suspending administration of Moderna’s COVID-19 vaccine for people under 18 years of age, while Sweden announced today that it is doing the same for people under 30, Reuters reports.

Both countries cited data showing a potential increased risk of rare inflammatory heart conditions known as myocarditis and pericarditis among younger people who receive the Moderna shot, and recommended that individuals in those age groups get the Pfizer/BioNTech vaccine instead. Canadian vaccine data showed increased cases of heart inflammation particularly in adolescents and young adults after receiving the Moderna COVID-19 vaccine Spikevax, according to Reuters. Health experts from both Sweden and Denmark maintain that the risk of either myocarditis or pericarditis after receiving Spikevax remains small.

The US Centers for Disease Control and Prevention notes that young males seem to be more at risk of the inflammatory conditions after receiving Moderna’s or Pfizer’s mRNA vaccines, and that patients who develop these conditions following COVID-19 vaccination tend to recover quickly. The agency continues to recommend that everyone 12 and older receive a COVID-19 vaccine, as the risks posed by COVID-19 far outweigh those associated with vaccination.

See “Moderna vs. Pfizer: Is There a “Best” mRNA Vaccine?

Denmark and Sweden are not alone, however; Norway had already recommended the Pfizer vaccine for men under 30 years old, according to Reuters. Finland is set to announce a decision tomorrow.

“Based on the precautionary principle, we will in future only invite children and young people to receive [the Pfizer] 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,” Swedish health authority Bolette Soeborg tells the Associated Press.

See “Blood Clot Risk From COVID-19 Higher than After Vaccines: Study

Sweden had previously rejected Moderna in favor of Pfizer’s Corminaty vaccine for children 12 to 15 years old, Reuters reported. “All in all, we see reason to choose the vaccine that we know the most about and that is most well-proven when it comes to vaccinating children between 12 and 15 years of age,” Anders Tegnell, state epidemiologist of the Public Health Agency of Sweden, told Reuters at the time.