Increased risk of myocarditis even after the third dose

Early in the pandemic, initial vaccination with two doses of an mRNA vaccine against COVID-19 was shown to increase the risk of myocarditis. The pharmaceutical world has highlighted this in several articles.

I showed The risk of side effects is higher among young people. It is also higher among boys and men than among girls and women. Because the increased risk is greater for the Moderna vaccine, it is no longer used for people under 30 years of age.

Now researchers in a new Northern European study suggest that there is an increased risk of developing myocarditis even after a third vaccine dose. The study is published in European Heart Journal.

Researchers there confirm Also, the individual's risk of developing myocarditis after vaccination (absolute risk), despite the increased risk, is still very small.

Study of increased risk of myocarditis

The medicines and public health authorities of Sweden, Norway, Denmark and Finland have conducted several joint studies on the safety of Covid-19 vaccines. On the Swedish side, the Medical Products Agency participated.

Researchers have used Data from national registries in the four countries. Data were thus collected on a total of 8.9 million people between the ages of 12 and 39 years. Researchers there studied how common it was to seek hospital care for myocarditis in the first four weeks after the third dose of the mRNA vaccine.

This was compared, among other things, to the incidence of myocarditis among the unvaccinated.

Reduced increased risk

The results show a pattern similar to that of side effects after primary vaccination. The risk of developing myocarditis is increased, and the Moderna vaccine gives a higher risk increase than the Pfizer/BioNTech vaccine, and boys and men are most at risk.

– However, the increase in risk is Less than the risk increase after doses 1 and 2, confirms Rikard Leung, professor and doctor at the Swedish Medicines Agency and responsible for the Swedish part of the study.

It expresses itself in a comment regarding one press release From the Swedish Medicines Agency.

However, the absolute risks were low

The comment can be explained by the fact that boys and men aged 12 to 39 years during the month following primary vaccination with the Moderna vaccine were more than twelve times at risk of developing heart disease than the unvaccinated. After the additional dose, dose 3, the risk was approximately six times higher than in unvaccinated individuals, an increase in risk of half.

thinks Rickard Leung One should also discuss not only the increase in risk, but also the level of risk involved.

Even if the risk increases, the absolute risk of myocarditis after vaccination is still very low, he says.

Continuous analytics

Absolute risk is a measure that indicates an individual's risk of developing myocarditis. According to the study, the side effect affects, for example, two boys or men between the ages of 12 and 39 for every 100,000 vaccinated with the Moderna vaccine. The corresponding figure for the Pfizer/BioNTech vaccine is 0.9 per 100,000 boys and men vaccinated.

Northern researchers She will continue her analytical work. Among other things, they will study the long-term prognosis of those with myocarditis.