COVID-19 rises risk of myocardial inflammation

There has been an increase in myocardial inflammations in Finland, but the cases are rare in relation to the total number of people vaccinated, according to the National Institute for Health and Welfare (THL).

These findings are in line with the results obtained in other countries and do not give reason to amend the THL recommendations for taking the first or second dose of COVID-19 vaccine, said the THL in a recent press release.

The THL has examined the incidence of myocardial inflammations requiring hospital treatment in patients who have received COVID-19 vaccines.

The prevalence of the inflammations was monitored in the health care registers for four weeks after the first and second dose of vaccine. THL has also examined the incidence of myocardial inflammation after COVID-19 infection.

In the United States and Israel, more cases of myocarditis have been diagnosed with people who have received an mRNA vaccine than the population on average.

Inflammations have been observed especially in young men after the second dose of vaccine. mRNA vaccines include Biontech-Pfizer’s Comirnaty and Moderna’s Spikevax.

Myocarditis also occur continuously in the population without the COVID-19 vaccination. Since the beginning of the COVID-19 vaccinations, 102 cases of myocardial inflammations have been diagnosed in unvaccinated men in Finland and 48 in unvaccinated women.

Also in Finland, myocarditis occur most in young men, whether they are vaccinated or not.

According to THL monitoring, vaccinated men and boys under 30 years of age were diagnosed with approximately four additional myocardial inflammations per 100 000 recipients of the mRNA vaccine. Cases found within four weeks of receiving the second dose of vaccine were included.

Since the beginning of the vaccinations, men and women who have received COVID-19 vaccines have been diagnosed with myocardial inflammations in Finland as follows:

After the first dose of vaccine, a total of 26 myocardial inflammations requiring hospital treatment have been diagnosed among about 3.8 million vaccine recipients. 22 cases have been reported in men and 4 in women.

After the second dose of vaccine, a total of 21 myocardial inflammations requiring hospital treatment have been diagnosed among about three million vaccine recipients. 13 cases have been reported in men and 8 in women.

It is not possible to compare the number of cases after the first and second doses and their proportion of the number of vaccines directly. This is due to the fact that four weeks have not yet elapsed since the last vaccination of all those who received the second dose.

‘The number of cases in Finland is very small in proportion to the number of vaccinated people, and it is not possible to draw definite conclusions on the level of risk. Despite the increased risk, the myocardial inflammations of vaccinated patients are rare in general after both the first and second doses of vaccine. The symptoms of myocardial inflammations diagnosed in young men are generally mild’, said Petteri Hovi, Senior Researcher at the National Institute for Health and Welfare.

Both vaccine doses in the basic vaccination series can still be taken normally. The second dose of vaccine strengthens and extends the protection provided by the first dose.

COVID-19 also increases the risk of myocardial inflammation. THL compared the incidence of myocardial inflammation in those aged 12 or over who had been infected with COVID-19 to those in the same age group who had not been infected. The risk of myocardial inflammation was similar between those who had been infected with COVID-19 and those who had been vaccinated. The same result has also been achieved in studies carried out in other countries.

Myocardial inflammation occurs more frequently after other infections, as well, such as seasonal influenza.