Results from a Nordic study examining the effectiveness and impacts of mRNA vaccines were released on 20 April 2022. The article, published in the medical journal JAMA Cardiology has already had over 130,000 views online.
The study involved a meta-analysis (combination of studies) on more than 23 million participants aged 12 years and over (81% of whom were vaccinated by the end of the study) from Denmark, Finland, Norway, and Sweden. Data was obtained from linked nationwide health registers across the four countries to assess the efficacy of mRNA technologies used during the pandemic.
Results were obtained by examining incident outcome events that were defined as the date of first inpatient hospital admission based on primary or secondary discharge diagnosis for myocarditis or pericarditis from December 27, 2020, through to 5 October 2021. Vaccination outcomes were followed for up to 28 days post-vaccination for the first and second dose.
The study found an increased risk of myocarditis and pericarditis associated with mRNA vaccines (Pfizer and Moderna), with risk highest within the first seven days after vaccination and increasing risk for all combinations of mRNA vaccines after the second dose. Young males aged between 16-24 years who had received two doses of the same vaccine were at the greatest risk of myocarditis, with this risk most prevalent after the second dose.
The findings support those conducted in the US, Israel, and Canada with these studies showing an increased risk of myocarditis after mRNA vaccines, with higher rates after the second dose, especially in younger men. A study of French participants resulted in similar findings with those receiving a Moderna vaccine more likely to experience myocarditis when compared to Pfizer, although further research is needed to further unpack these findings.
Other studies recently published also highlight the risks posed by mRNA vaccines. Results of a small study found that mRNA covid vaccinations could elicit ‘immune-mediated hepatitis’ and liver inflammation. Although liver inflammation may also be observed after covid infection, the research highlights the need for urgent, thorough, and transparent reporting of study findings.
An additional study noted the potential for mRNA SARS-CoV-2 vaccines to trigger systemic lupus erythematosus (SLE) as well as inducing the development of new-onset rheumatic disease. Decision-makers should provide transparent, open, and plain language summaries of how these studies have been used to support ongoing decisions around vaccinations.