Cardiomyocarditis is a known uncommon side effect following COVID-19 vaccination. They are described mainly after vaccination with a mRNA vaccine, most commonly after dose #2. The age- and sex distribution are similar to that of other cardiomyocarditis (which tend to be viral infections), i.e., the highest prevalence is in 12-39 year old men. How this side effect develops after vaccination, i.e. the triggering mechanism of the inflammation, is not yet known.

Little has been observed of cardiomyocarditis or pericarditis after booster doses (third dose) of COVID-19 vaccines, but it has generally not been recommended to revaccinate those who have experienced this side effect. Recently, however, authorities have recommended weighing the risk of COVID-19 infection against the risk of vaccination for individuals in this situation.

In consultation with cardiologists in Iceland:

• As is not recommended, revaccination of individuals with confirmed myocardial or pericarditis in general after vaccination with mRNA vaccine is not recommended.

• Individuals who are considered at increased risk of serious illness due to COVID-19 may discuss further vaccination with the physician who is dealing with the underlying disease, who can then consult a cardiologist if considered necessary.

  • If a decision is made to revaccinate, the vaccine considered most unlikely to cause cardiomyocarditis or pericarditis should be used at any given time.

    Moderna vaccines should not be used for individuals with a history of cardiomyocarditis or pericarditis following COVID-19 vaccination.