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Inflammation of the heart muscle (myocarditis): What is the risk of Covid-19 and the coronavirus vaccination?

"All the data indicating that clinically proven myocarditis after vaccination with an mRNA vaccine is very rare overall," says cardiologist and pharmacologist Prof Thomas Meinertz. | © German Heart Foundation

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The German Heart Foundation provides information on the risks of myocarditis from Covid-19 and mRNA vaccination. One expert says: "The health risk from a Covid-19 infection - in every age group - is much higher than the risk of myocarditis from mRNA vaccination."

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The inflammation of the heart muscle in prominent footballers such as Alphonso Davies has once again raised the question: How dangerous is Covid-19 for the heart - even in younger people? And how high is the risk of heart muscle inflammation (myocarditis) or pericarditis following vaccination with an mRNA vaccine?

Risk of myocarditis due to Covid-19 at least four times higher than with vaccination

 "The occurrence of vaccine-induced myocarditis or pericarditis is extremely rare," emphasises cardiologist Prof. Dr Thomas Meinertz from the Scientific Advisory Board of the German Heart Foundation. At the same time, he points out: "The health risk from a Covid infection - in any age group - is much higher than the risk of myocarditis/pericarditis from vaccination with an mRNA vaccine." The risk of myocarditis due to Covid-19 disease is at least four times higher than that of vaccine-induced myocarditis, as studies from the USA, Great Britain and Israel show (1, 2, 3). In addition, the risk of other cardiac risks, such as arrhythmias and heart attacks, as well as acute kidney damage and pulmonary embolisms, is significantly higher for unvaccinated people (3, 5).

"We are therefore appealing to everyone, especially older people and those at risk of a severe course of Covid-19, to get fully vaccinated or to have their vaccination protection refreshed with a booster," says the Heart Foundation expert.

Current data on vaccine-induced myocarditis

The incidence of vaccine-induced myocarditis or pericarditis caused by an mRNA vaccine averages one to ten cases per 100,000 vaccinations (1). Data from over 300 million Covid-19 vaccinations worldwide in various countries is now available to assess the risk situation. This also allows a reliable statement to be made on the risk-benefit ratio of vaccination against Covid-19 with the aim of preventing severe disease progression and death from SARS-CoV-2 infection. "The risk of severe acute heart damage is apparently significantly greater with an infection with the SARS-CoV-2 pathogen than with a vaccination with an mRNA vaccine to protect against Covid-19," says Meinertz, referring to a large number of studies, including an analysis of data from around 1, 7 million people with and without vaccination from Israel (3) and a study from the UK with data from 38 million vaccinated people, which was compared with cases of myo-/pericarditis and cardiac arrhythmias as well as SARS-CoV-2 infection data (1).

Vaccination data for Germany show that although the risk of myocarditis after mRNA vaccination is present, it is very low. As emphasised by the Paul Ehrlich Institute (PEI) in its December 2021 safety report (4), in line with other international data (including Israel, USA, Europe), cases occur predominantly in male adolescents and young adults up to 29 years of age - usually within a few days and more frequently after the second dose of an mRNA Covid-19 vaccination. According to the PEI, the vast majority of patients with myo-/pericarditis after vaccination with mRNA vaccines respond well to treatment and rest and feel better quickly, even if more severe courses have been observed in individual cases. In general, patients and doctors/medical professionals should look out for signs of myocardial inflammation after a Covid-19 vaccination, the PEI advises.

What are the typical symptoms of myocarditis?

There is no single leading symptom of myo-/pericarditis. "In the case of Covid-19 disease, the first signs of inflammation of the heart muscle or pericardium are lost in the general symptoms of infection and are not related to the heart," explains cardiologist Meinertz. You should be alert if these symptoms persist or reappear after the symptoms of infection (fever, dizziness, muscle pain, diarrhoea) have subsided:

  -   Shortness of breath on exertion,
  -   palpitations,
  -  heart palpitations (arrhythmia),
  -  heart pain (especially with pericarditis)
  -  unexplained tiredness and fatigue,
  -  physical weakness.

As unspecific as the symptoms are, the diagnosis is difficult, especially in mild forms. To clarify the suspicion, the doctor will initially use an ECG, X-ray and echocardiography. Magnetic resonance imaging of the heart (MRI) and blood tests for the laboratory value troponin are also important in the further course.

Take it easy with myocarditis

Intensive sporting activities should be avoided for around six months after myocarditis is suspected and should only be resumed after a cardiological check-up with normal findings. The long-term prognosis after acute viral myocarditis with no significant complications is predominantly favourable. Complete recovery can be assumed in around 70 % of patients. In some patients, mild symptoms remain due to scarring in the heart muscle, including mild arrhythmia. However, the prognosis is significantly worse for patients with pre-existing severe heart failure.

Suspected cases mainly in young men after Covid-19 vaccination

According to the PEI safety report (4), 1,554 suspected cases of myo-/pericarditis - regardless of the causal relationship with the respective vaccination - have been reported for a total of over 107 million doses of Comirnaty/Biontech and Spikevax/Moderna vaccines administered in Germany up to and including 30 November 2021. According to calculations for Comirnaty/Biontech, the overall reporting rate for all age groups and all vaccinations was just under 0.8 suspected cases per 100,000 vaccinations in women and 1.5 suspected cases per 100,000 vaccinations in men. For Spikevax/Moderna, the reporting rate was 1.28 suspected cases per 100,000 for women and 4.6 for men.

The reporting rate of myo-/pericarditis for Comirnaty/Biontech in young men (18-29 years) after the second vaccination is around nine suspected cases per 100,000 vaccine doses (women of the same age 1.5 cases). For Spikevax/Moderna, the reporting rate was highest in young men (18-29 years) after the second dose, with over 25 suspected cases per 100,000 vaccinations (women just under six cases). The Standing Committee on Vaccination (STIKO) therefore only recommends the Comirnaty vaccine for people under the age of 30 as a precautionary measure.

In addition to the suspected cases reported in the PEI report, there are now a number of studies that have analysed clinical cases: "All data indicate that clinically proven myocarditis after mRNA vaccination is very rare overall. In addition, 95 per cent of cases were described as mild with a mostly short hospital stay," says cardiologist and pharmacologist Meinertz.

Conclusion based on practical experience

The following common findings can be gleaned from the study data to date, which have also been repeatedly confirmed by scientists in practice:

- The risk of myocarditis following mRNA vaccination is present, but very low.
- The risk is lower with the Comirnaty/Biontech mRNA vaccine than with the Spikevax/Moderna vaccine.
- It affects more young men under the age of 30 than women (highest risk between 15 and 29 years).
- Complaints and symptoms of myocarditis usually occur within a few days after the vaccination (usually the second).
- The course of myocarditis is generally described as mild with no consequential damage.
- The health risk from a Covid infection is estimated to be much higher - in every age group - than the risk of myocarditis/pericarditis from vaccination with an mRNA vaccine.

Background: What is myocarditis/pericarditis?

Myocarditis is an inflammatory disease of the heart muscle (myocardium) in which pathogens (predominantly viruses) frequently attack the heart muscle tissue. They penetrate the cells, which can lead to the destruction of the heart muscle tissue. The process can be localised in the heart, but in the worst case it can also affect the entire heart muscle. The body's own immune defence can often counteract this process and achieve a cure. The type, extent, duration and remaining final state of this inflammatory process (inflammation) and tissue damage vary greatly from individual to individual, making the course and prognosis of myocarditis difficult to predict. There are basically three different forms of myocarditis:

- Subclinical myocarditis (often not even noticed, usually heals without serious complications)
- Acute myocarditis (classic form with acute impairment of heart function)
- Chronic myocarditis (inflammatory processes in the heart tissue continue to be more or less active)

In pericarditis, inflammatory processes similar to those in myocarditis occur and in this case affect the connective tissue envelope (pericardium), which completely surrounds the heart and keeps it in shape. The pericardium is directly adjacent to the heart muscle tissue. Here too, a distinction is made between an acute and a chronic course.


(1) Nat Med 2021

(2) JAMA 2021

(3) NEJM 2021

(4) Paul Ehrlich Institute safety report (in German only)

(5) The Lancet 2021

Source: press release German Heart Foundation (in German only)