The United States Centers for Disease Control and Prevention (CDC) has announced that the Moderna COVID vaccine "may pose" a higher risk of heart inflammation in some age groups than the vaccine produced by Pfizer BioNTech.

According to data from the Vaccine Safety Datalink (VSD), there are 97.3 cases of heart inflammation per million vaccine doses for Moderna's product (after a second injection) as opposed to 81.7 cases per million for the Pfizer product. While the CDC claims that most cases of myocarditis or pericarditis are "mild" and that "most people" recover after receiving such a diagnosis, a significant proportion of people are hospitalized due to heart inflammation (which categorizes the condition as serious) and many never make a full recovery.

A year ago, following warnings from U.S. servicemen that a higher-than-expected rate of heart inflammation was found following COVID vaccination, an expert panel advising the CDC concluded that the rate was just 12.6 cases per million.

The VSD data are largely based on reports submitted to the CDC's VAERS vaccine injury reporting system, which itself is known to suffer from underreporting, partially due to the fact that submitting a report to VAERS is a complicated procedure that laymen are usually deterred by.

The CDC announcement comes as the FDA is meeting to discuss approval of Moderna's vaccine for children between the ages of 6 and 17.

In Europe, several countries including Sweden, Denmark, Iceland, and Finland moved to either "pause" or "advise against" younger people receiving the Moderna vaccine as early as last October.