Covid-19 and myocarditis: what do the numbers say?

From the first cases of Covid-19, it appeared that the heart was a prime target for the coronavirus, with the risk of serious cardiovascular disorders. A significant number of hospitalized patients thus show signs of heart damage, and many remain affected even after their infection is over.

Whether we are discussing the safety of vaccines anti-Covid and their risk to cardiovascular health is hardly surprising. L’cardiac arrest highly publicized Danish footballer Christian Eriksen in the middle of the Euro tournament launched a persistent myth about the dangers of vaccination for athletes. The controversy over Covid vaccines focuses on the risk of myocarditis after vaccination, especially among young people. But what does the data say?

What is myocarditis?

Myocarditis is a inflammation from heart muscle usually caused by a virus like influenza, coxsackie, hepatitis or herpes. Other causes include bacteria, the fungal infections, the toxins, chemotherapy and autoimmune diseases.

Some viruses cause direct damage to the heart, while others damage it indirectly via the immune system. Indeed, the latter reacts to infections by releasing into the body molecules called cytokines that regulate the immune response. However, it happens that the cytokine levels reach too high levels, and this ” wave of cytokines will damage the heart muscle.

Myocarditis in numbers

Before Covid-19, theimpact myocarditis was located between one and ten cases per 100,000 people per year. Interestingly, the highest risk was in men between the ages of 18 and 30, particularly active, healthy individuals. According to the US Public Health Agency (CDC), the risk after a Covid-19 infection is around 146 cases per 100,000 people. The greatest risk concerns men, mainly adults over 50 and children under 16. A typical case is that of footballer Alphonso Davies, 21, of the Canadian national team, who suffered heart inflammation after contracting the coronavirus.

Post-vaccination myocarditis

Myocarditis secondary to vaccination anti-Covid is rare and the risk is much lower than for myocarditis linked to Covid-19. According to one israeli study, the post-vaccination myocarditis rate is 2.13 cases per 100,000 vaccinated, i.e. within the normal pre-Covid-19 frequency range. This result agrees with other American and Israeli studies which situate the overall incidence of post-vaccination myocarditis between 0.3 and 5 cases per 100,000 people.

After vaccination with RNA messenger, the highest incidence of post-vaccination myocarditis occurred in men under 30 three to four days after the second dose. Among minors, pediatric data indicate a median age of 15.8 years, with 90.6% male, white (66.2%) or Hispanic (20.9%). For this age group, reliable data on booster injections are not yet available.

Most studies show a clear benefit of vaccination with mRNA regarding myocarditis. A single study, conducted by Martina Patone’s team from Oxford University, concludes more equivocally for individuals under 40 years of age. This is based solely on myocarditis rates. However, taking into account all the harmful effects, cardiac or not, of Covid-19, it remains very advantageous to immunize younger people with vaccines other than Moderna – the latter, according to research, would still present higher risk of myocarditis than Pfizer.

Repair the damage

The treatment of myocarditis varies according to its gravity. In its mild form, an adult only needs rest and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. More severe cases require medication or even ventricular assist, a surgically implanted mechanical device. If this treatment does not work, it is then necessary to resort to the transplantation cardiac.

As part of a multicenter study of patients under the age of 21, those with symptoms mild were receiving no anti-inflammatory treatment or only NSAIDs. Patients with more severe symptoms could be given stronger treatments, such as immunoglobulin intravenous, glucocorticoids or colchicine, in addition to NSAIDs.

Is it serious doctor ?

More than 80% of cases of myocarditis unrelated to Covid-19 or vaccination recover without problem, while 5% of patients die from it unless they receive a heart transplant within a year. Adults who develop myocarditis following a Covid-19 infection fare worse than those with myocarditis unrelated to Covid-19. Their death rate is higher.

It should be noted that in addition to myocarditis, Covid-19 causes other heart diseases and their prognosis, on the other hand, is less favorable than for cases not associated with infection.

As for post-vaccination myocarditis, the vast majority of cases are mild and heal quickly. In adults, 95% of cases are considered mild. Similarly, in children — with 98.6% mild cases and no need for mechanical heart support. All the children affected in the heart saw their cardiac function normalize completely during the follow-up and there are no deaths.

The take home message

Given the constant evolution of pandemic world and knowledge, it can be difficult for the public to assimilate all the information about the risks and benefits of vaccines. It is therefore useful to seek the advice of medical organizations whose mandate is to protect the health and well-being of society.

Considering all the research available, organizations like the American Heart Association (AHA), the Canadian Cardiovascular Society, the Heart and Stroke Foundationstroke of Canada, the Canadian Society of pediatrics and the American Academy of Pediatrics (APA) encourage all eligible individuals to get vaccinated against Covid-19. It is this message that we should all take to heart.

Cases of myocarditis identified after injection of mRNA vaccines

In the United States, the CDC (Center of Disease Control and Prevention) reports the occurrence of a handful of cases of myocarditis after the injection of the mRNA vaccines of Pfizer and Moderna. For the moment, it is impossible to say if the two events are linked.

Article of Julie Kern, published on May 24, 2021

In the United States, the vaccine safety committee meets weekly to review side effects. Covid-19 vaccines after their emergency use authorization has been issued. At their last meeting on May 17, 2021, several members of the committee presented cases of myocarditis following the injection of mRNA vaccines, from both Pfizer and Moderna. Investigations have not yet been able to establish a strict link between vaccination and the onset of myocarditis. It could just be a coincidence. Most of those affected are being treated in hospital and their life prognosis is not at stake. The doctors were able to draw a very rough composite portrait of the people most at risk.

Young men are concerned

Myocarditis appears in the four days following the injection of the vaccine, more frequently after the second dose. The side effects are usually more intense after this one. Those affected are mostly young men, adolescents or young adults. For now, the Center of Disease Control and Prevention (CDC) indicates that the incidence rate of myocarditis since the start of the vaccination campaign is not higher than usual.

The precise number of cases has not been communicated, it is “relatively low” among the 253 million vaccine doses Pfizer and Moderna, distributed as of May 10, 2021. The latest ANSM pharmacovigilance report, dated May 21, 2021, reports no cases of myocarditis in France. Further research will be launched to link, or not, these cases to mRNA vaccines and adjust their management. The occurrence of these cases does not, to date, call into question their use.