Young men who receive the Moderna COVID-19 vaccine are at higher risk of developing a rare case of heart inflammation than those who received the Pfizer-BioNTech vaccine, researchers revealed on Thursday.
Researchers revealed the data at a meeting of the Centers for Disease Control and Prevention’s (CDC) advisory committee to discuss approval of booster doses for the Moderna and Johnson & Johnson shot.
A CDC official presented data that showed young men under the age of 30 who receive the Moderna vaccine have experienced a slight uptick in myocarditis and pericarditis cases.
This is the first data that show an increased risk in one of the vaccines when compared to the other.
However, officials stand by the safety of the vaccine, and still recommend it for use as the benefits heavily outweigh the potential risks.
Health officials in Nordic countries have made a different choice, though, with Denmark, Finland, Iceland and Sweden all restricting use of the Moderna jab among young people.
People aged 18 to 29 who received the Pfizer-BioNTech vaccine (left) were less likely to develop myocarditis than people who received the Moderna vaccine (right). The chart shows rates of the condition per every one million recipients of that vaccine in each age group. The Moderna vaccine is not available to Americans under the age of 18
For every one million people who received each jab, there were 21.5 more cases of heart inflammation that included pericarditis in males 18 to 39 that received the Moderna jab, and 19.1 more cases without pericarditis for everyone one million who receive the shot when compared to the Pfizer vaccine
The CDC found that 36.8 out of every one million men aged 18 to 24 who received the Pfizer vaccine, and 10.8 of every one million aged 25 to 29, developed myocarditis.
Moderna recipients had higher rates of the condition, with 38.5 out of every one million males aged 18 to 24, and 17.2 of every million aged 25 to 29, developing the condition.
After age 29, the rate of heart inflammation as a vaccine side-effect significantly falls off.
Researchers at the CDC also calculated the total number of excess cases Moderna recipients suffered compared to Pfizer recipients.
They found that for every one million men aged 18 to 39 who received the Moderna vaccine, there were 21.5 more cases of myocarditis with pericarditis than there were in every one million who received the Pfizer jab.
For cases without pericarditis, there were 19.1 excess cases for every one million vaccine recipients.
The officials note that there was no difference in the severity of the myocarditis cases, though.
American health officials have long recognized the risk of heart inflammation as a potential side-effect of the Pfizer and Moderna vaccine in young me – with the CDC issuing a warning in June.
The Moderna vaccine is still considered safe and effective despite this data, though, as the cases are still few and far between with less than 0.01 percent of people who get the shot developing myocarditis.
Some Nordic nations are being cautious with the vaccine in response to this type of data, though.
Earlier this month, Swedish health officials gathered unpublished data that showed the Moderna vaccine in particular put its recipients at risk of developing myocarditis after receiving the shot.
In the time since, Denmark, Finland, Iceland and Sweden have all restricted use of the shot in young people, citing the unpublished data.
Norway is also now only recommending the Pfizer vaccine to young people.
While myocarditis will often resolve itself, it can be dangerous.
Heart inflammation can often lead to fatigue, shortness of breath and chest pain for patients.
People with inflamed hearts are at a higher risk for heart failure, heart attacks and strokes.
Attempting strenuous physical activity with an inflamed heart could also potentially lead to sudden cardiac arrest, or even death.
In four Nordic nations, use of the Moderna vaccine has been restricted among young people due to unpublished Swedish data that shows the jab puts people at an increased risk of heart inflammation. Pictured: A man in Helsinki, Finland, receives a shot of a COVID-19 vaccine on December 27, 2020