Covid-19, Vaccination and risks of Myocarditis

Studies suggest that upto 18% of patients who are hospitalised with COVID-19 have evidence of myocardial injury as measured by elevated Troponins ie they have evidence of a myocarditis. Remember this is 18% of hospitalised patients i.e patients who by definition have a more severe form of infection. There are some data to give us a guide as to how common myocarditis is in the whole population of patients who get COVID and there was a study looking at younger patients and they estimated that the incidence was about 500 cases per million patients in the age group of 12-19 years. This equates to a percentage of 0.05. I am sure these are not completely accurate data but these are the data that we have. There was another study that looked at 1597 athletes and they concluded that based on symptoms, the incidence of myocarditis was 0.31% and if you used MRI scanning then upto 2.3% of these patients had myocarditis. In 40% of these patients the myocarditis had completely resolved on repeat imaging within 4-10 weeks.

Can the vaccines cause myocarditis?

There is some suggestion that the Pfizer and Moderna vaccines may be associated with a slightly higher incidence of myocarditis. As these particular vaccines have been used extensively in the US and Israel most of the data comes from these countries. In the USA, 296 million doses of thes mRNA vaccines have been given (by June 2021) and there were 1226 reports of myocarditis after vaccination. In the US they clumped myocarditis, pericarditis and myopericarditis under the term myocarditis. In those patients, the medican age was 26 years and the time to onset was a median of 3 days after vaccination. In Israel, over a 6 month period there were 148 reports of myocarditis with about 5 million vaccinations. Again the incidence was higher in young males and usually after the second dose. In the UK, there have been 149 cases of myocarditis and 129 reports of pericarditis with the Pfizer vaccine. 82 reports of myocarditis and 140 reports of pericarditis with AZ abd 25 reports of myocarditis and 22 reports of pericarditis with the Moderna vaccine Overall rates are 4.3 cases/million doses of myocarditis and 3.8 cases per million of pericarditis with Pfizer; 1.7/million doses of myocarditis and 3.0/million of pericarditis with AZ and 14.7/million doses of myocarditis and 13.0/million dose of pericarditis with Moderna.

What is the outcome of vaccine associated myocarditis?

There was an analysis of the patients in the US and they found that 96% of these patients with myocarditis had to be hospitalised but fortunately there were no deaths. However there were in the Europea economic area 5 deaths were reported but in generally older patients with more comorbidities. The general consensus is that the prognosis is good. But we need to study patients over a longer period of time to understand if there are any issues with regards to an increased incidence of heart failure or heart rhythm disorders.

What does all this mean?

The data should not dissuade anyone who is considering the vaccine to have it. In fact it is estimated that the risks of developing myocarditis from COVID itself is about 5x greater than from the vaccine. However if you develop symptoms of chest pain, breathlessness or palpitations within 2 weeks of receiving the vaccine then it is important to seek medical advice and have an ECG, blood tests for Troponin and an echocardiogram.


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