Study: Moderna More Likely To Cause Myocarditis Than Pfizer

UNSPLASH ILLUSTRATION

JAKARTA - Moderna's COVID-19 vaccine is up to four times more likely to cause inflammation of the heart muscle, a very rare side effect, than the Pfizer-BioNTech vaccine, according to a Danish study published in the British Medical Journal.

The study, which involved nearly 85 percent of Danes or 4.9 million people aged 12 years and over, investigated the link between an mRNA-based COVID-19 vaccine and inflammation of the heart also known as myocarditis or myopericarditis.

Previous studies in Israel and the US indicated an increased risk of post-vaccination cardiac inflammation with the mRNA vaccine developed by Pfizer-BioNTech and Moderna.

"Vaccination with mRNA-1273 (Modern vaccine) was associated with a significantly increased risk of myocarditis or myopericarditis in the Danish population," the study said.

However, the overall risk of developing heart inflammation from vaccines based on mRNA technology is small, according to a study by Danish Statens Serum Institute researchers.

"In general, rates of myocarditis or myopericarditis were about three to four times higher for the mRNA-1273 vaccination (Moderna) than for the BNT162b2 vaccination (Pfizer-BioNTech)," the study said.

Researchers found only 1 case per 71,400 Pfizer-BioNTech vaccine recipients and 1 case per 23,800 Moderna vaccine recipients. Most cases have mild symptoms, he said.

The Pfizer-BioNTech vaccine was only associated with a higher risk of heart inflammation among women, according to the study. This contradicts the results of Israeli and US studies.

Researchers say the difference could be explained by the average age of the population being vaccinated, the interval between the first and second doses or because fewer Danes have tested positive for COVID-19.

"Our findings do not in general ignore the many benefits derived from vaccination," study author Anders Hviid said in a statement.

"It must be remembered that the alternative to being infected with COVID-19 may also involve the risk of inflammation of the heart muscle," he said.