Various reports from Canada, Israel and the US have indicated that there may be an increased risk of myocarditis following the administration of mRNA vaccinations against SARS-CoV-2, the virus that causes COVID-19. Furthermore, preliminary data from studies in Canada and France have suggested that myocarditis incidence rates may be higher following the Moderna vaccine than the BioNTech/Pfizer jab. ... To investigate further, epidemiologist Professor Rickard Ljung of the Swedish Medical Products Agency and his colleagues studied health data on a total of some 23.1 million people from Denmark, Finland, Norway and Sweden from late December 2020 to early October 2021....