2023-05-09 14:27:11
Updated on 05/09/2023 18:05
Overall they are rare. But among the known cases, it is mainly male adolescents who are struggling with heart muscle inflammation after a corona infection or vaccination. Researchers have now discovered the reason for this.
In very rare cases, the heart can become inflamed during viral infections or after vaccinations. This has been known for a long time and also applies to Covid-19 and the vaccination against Sars-CoV-2. A multidisciplinary team from the Yale University School of Medicine in New Haven (USA) has now found evidence of why heart tissue can become inflamed after the corona vaccination. The researchers, including the immunologists Akiko Iwasaki and Carrie Lucas, published their study results on May 5, 2023 in the journal “Science Immunology”.
Why the study is important
Every vaccination activates the immune system. This is desired because the body produces defense molecules – these are antibodies – and forms an immune memory through contact with the weakened pathogen or its individual components. In very rare cases, the immune system reacts to a vaccination, for example against tetanus, meningococcismallpox or just Covid-19, much too severe: the heart muscle and/or the pericardium become inflamed.
After the corona vaccination, the frequency of such myocarditis or pericarditis depends heavily on the age and sex of the vaccinated person. Recent figures from the USA According to the study, boys in the age group between twelve and 17 years are most frequently affected with almost 36 cases per 100,000 vaccinates. Across all age groups, the frequency in boys or men is 0 to almost 36 per 100,000 vaccinates, in girls or women 0 to almost 12 cases per 100,000 vaccinates.
It has not yet been clarified why the heart tissue in particular becomes inflamed and why it primarily affects boys or male adolescents. Some suspect one Autoimmune reaction against the body’s own characteristics could be the cause. Others have a kind hypersensitivity reaction suspected to involve a group of immune cells called ‘eosinophils’. “We wanted to understand how these complications can occur in order to further reduce the risk of future vaccinations,” said Carrie Lucas at a press event organized by the American Association for the Advancement of Science (AAAS) on the occasion of the current publication.
What the researchers did
The Yale team examined blood samples from 23 young people between the ages of 13 and 21. 20 of them were boys or young men. One to four days after the second Covid vaccination with an mRNA vaccine, all those affected had developed chest pains and headaches, felt weak and short of breath, complained of an irregular heartbeat and nausea – all symptoms of myocarditis.
In the hospital they were given medication to stop inflammation. After six days at the latest, everyone was able to go home. The complaints had improved significantly; however, signs of tissue thickening in the heart muscle were still found in most of those affected months after the vaccination. This could limit the function of the organ and must be monitored further by a doctor.
The team examined the blood for antibodies, various immunological messenger substances and the presence of various immune cells. “We used every available immunological tool to understand what’s happening,” Akiko Iwasaki said at the AAAS press briefing.
What the results look like
The researchers found no signs of an excessive antibody response in response to the vaccination and no antibodies directed against molecules in the heart tissue. There was also no evidence of a hypersensitivity reaction to components of the vaccine.
In the blood of those affected, on the other hand, there were greatly increased amounts of certain messenger substances – a sign of an unusually violent reaction of the innate immune system to the second vaccination. The flood of messenger substances triggered natural killer cells and so-called cytotoxic T-cells, which otherwise only become active after being “targeted” by cells of the innate immune system and in a strictly controlled manner – but here they apparently damage the heart.
In addition, another activated group of immune cells, so-called monocytes, appeared in the blood in increased numbers. They commonly aid in wound healing and help repair tissue. However, these immune cells can also contribute to the fact that organs only function to a limited extent after inflammation because the tissue hardens or thickens.
What the results mean
According to the study, the work is a prerequisite for further improving the safety of corona vaccines or mRNA vaccines in general. This type of vaccine will certainly continue to gain in importance for clinical practice in the future. The better one understands the wrong reaction to the vaccination, the more likely it is to be able to avoid it. The researchers are also looking for blood values, so-called biomarkers, which can indicate vaccination complications in good time.
However, the vaccination regime for risk groups may also have to be adjusted: experts are discussing whether it makes sense to wait longer between the first and second Covid vaccination, for example eight weeks instead of four weeks as before. And whether reducing the vaccine dose can reduce the risk of myocarditis.
Also read: Post-Covid expert: Doctors prescribe these drugs for symptoms
What the study makes no statements about
The study results do not provide any answers to the questions as to why the heart and especially boys and young men are affected. Whether hereditary factors or the hormone testosterone play a role can only be guessed at. It also remains unclear what exactly triggers the violent reaction in the vaccine: Is it the mRNA? Or is it the small fat globules in which the mRNA is packaged?
Actually, larger studies would have to follow to confirm the results and further clarify the open questions. But that won’t be easy. Fortunately, it is becoming increasingly difficult to find participants for such studies, says Akiko Iwasaki – simply for the reason that heart muscle inflammation hardly ever occurs after the corona booster vaccination.
Sources used:
- ScienceImmunology: “Cytokinopathy with aberrant cytotoxic lymphocytes and profibrotic myeloid response in SARS-CoV-2 mRNA vaccine–associated myocarditis”
- PubMed: “Eosinophilic myocarditis temporally associated with conjugate meningococcal C and hepatitis B vaccines in children”
- PubMed: “Cardiac Complications After SARS-CoV-2 Infection and mRNA COVID-19 Vaccination”
- The New England Journal of Medicine: “IL-1RA Antibodies in Myocarditis after SARS-CoV-2 Vaccination”
- MDPI: “Hypersensitivity Myocarditis after COVID-19 mRNA Vaccination”
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