Which groups of people are susceptible to myocarditis after Covid-19 vaccination?

Myocarditis is a dangerous cardiovascular disease. Acute myocarditis causes a rapid decline in the contractile function of the heart muscle and as a result, the patient must be hospitalized with dangerous complications such as arrhythmia, acute heart failure or even death.

Current treatments for acute myocarditis are not very effective and sometimes patients need mechanical cardiac support devices or heart transplants. Patients can develop myocarditis due to Covid-19 infection or as a result of vaccination.

Which vaccines cause acute myocarditis?

On June 25, 2021, the US Food and Drug Administration (FDA) issued a warning about a side effect of two types ofVaccineThe most widely administered vaccine in the United States from Pfizer/BioNTech and Moderna is acute myocarditis.

What is special is that both of these vaccines are prepared based on the same mRNA technology, so many questions arise as to whether only these two vaccines cause acute myocarditis or vaccines prepared using other technologies also have the risk of causing acute myocarditis?

Israel was the first country to find a link between vaccines (from Pfizer/BioNTech and Moderna, which use mRNA technology) and myocarditis. The Israeli Ministry of Health said it had recorded 148 cases of myocarditis after Covid-19 mRNA vaccination in the past 30 days.

Illustration of myocarditis

In the United States, between December 2020 and May 2021, when the Covid-19 vaccine was first administered, only 148 cases of post-vaccination myocarditis were recorded. However, as states expanded their vaccination campaigns to the general population, from April 2021 to present, the Vaccine Adverse Event Reporting System (VAERS) has recorded 1,226 cases of post-vaccination acute myocarditis/pericarditis reported out of a total of 318 million doses of vaccine administered, or a rate of 3.8/1,000,000 people.

This side effect of vaccines based on DNA technology or inactivated viruses has not been recorded in the world medical literature.

Who is at higher risk for myocarditis?

Although statistical models based on clinical trials of mRNA vaccines predicted rates of myocarditis, data from the US Centers for Disease Control and Prevention (CDC) showed that the rate of myocarditis after vaccination was up to 3-4 times higher in younger people.

The median age of the group of people with myocarditis after vaccination was 12-50 years old, with the majority of cases concentrated in the age group of 16-28 years old. Of the 484 cases recorded in patients under 30 years old, 323 were diagnosed with myocarditis/pericarditis or both, and 309 were hospitalized. As of June 11, 2021, 295 cases were discharged from the hospital, and 9 cases continued to be monitored in the hospital, including 2 cases in the intensive care unit.

Myocarditis occurs after which injection?

Most of the cases were recorded after the second dose of vaccine. Of these, 80 cases were recorded with symptoms on the day of vaccination, about 540 cases recorded symptoms in the first 4 days after vaccination.

The proportion of men is higher than that of women, with 66% in the first dose and 80% in the second dose. The rate of myocarditis in the second dose is higher because the immune system has memorized the viral antigen from the first injection. When the second dose is given again, T lymphocytes directly destroy cells with mRNA from the vaccine, causing a very strong inflammatory reaction.

Families should be with their children 24/7, at least for the first 3 days after Covid-19 vaccination, to promptly detect dangerous signs after vaccination.

There is currently no official report on the cause of myocarditis after vaccination with the Covid-19 mRNA vaccine. Currently, there is only one study from Israel on the relationship between myocarditis and the COVID-19 vaccine on 500 patients, with official results expected to be announced by April 2022.

Young people have very strong immune systems, so after vaccination, the immune system secretes many immune and anti-inflammatory factors, which are released into the blood, travel to the heart, causing edema and myocarditis. Men are more susceptible to myocarditis because men have higher levels of testosterone in their blood, which increases inflammation and fibrosis.

Symptoms of acute myocarditis after Covid-19 vaccination

The symptoms recorded include: chest pain, shortness of breath, palpitations. Some abnormal tests such as arrhythmia, ST-T segment recorded on electrocardiogram and increased cardiac enzymes indicate myocardial necrosis. The above symptoms and clinical signs are typical of myocarditis.

Who should not get the Covid-19 vaccine?

This is a difficult question to answer. The US Food and Drug Administration (FDA) itself has not issued a specific recommendation. They say that this side effect is insignificant compared to the number of people who receive the vaccine and that the majority of patients have mild or moderate symptoms without any treatment.

Only people with a history of myocarditis or heart failure due to myocarditis appear to be advised against receiving the Pfizer/BioNTech and Moderna vaccines because of a possible increased risk of recurrent myocarditis.

Should we be concerned about this myocarditis complication?

Currently, no side effects of myocarditis have been recorded with other vaccines except for Pfizer/BioNTech and Moderna vaccines. Vietnam still mainly uses AstraZeneca vaccines based on vector technology, so no cases of myocarditis complications have been recorded.

However, when Pfizer/BioNTech and Moderna vaccines are imported in large quantities and are widely vaccinated, our knowledge will become necessary to be able to warn and handle them effectively in a proactive manner.