While the overall benefit of mRNA vaccines in the fight once morest the Covid-19 pandemic has been clearly established to date, myocarditis has been repeatedly listed in the literature as an undesirable but rare side effect of the administration of mRNA vaccines.
In order to better understand the clinical consequences of these myocarditis, a study published in the BMJ was conducted in the four Nordic countries (Denmark, Finland, Norway and Sweden) to compare the clinical course of these myocarditis with those associated with SARS-COV-2 infection or so-called conventional ones.
Of a cohort of 23 million subjects, 7292 patients were hospitalized for a new onset of myocarditis between 2018 and 2022, with 530 (7.3%) cases associated with mRNA vaccines, 109 (1.5%) cases associated with SARS-COV-2 infection and 6653 (91.2%) cases of conventional myocarditis.
After 90 days of follow-up, 62 people with post-vaccination myocarditis (VMP) were in intensive care, compared to 9 with post-infection myocarditis (MPI) and 998 with conventional myocarditis (CM). This places the relative risk of resuscitation compared to the conventional myocarditis group at 0.79 (95% CI 0.62 to 1.00) for the MPI group and 0.55 (95% CI 0.30 -1.04) for the MPV group.
27, 18, and 616 patients were diagnosed with heart failure or died in the MPV, MPI, and MC groups, respectively. The relative risk of developing heart failure within 90 days compared to the CD group was 0.56 (95% CI 0.37 to 0.85) for the MPV group and 1.48 (0.86 to 2.54 ) for the MPI group. The relative risk of death was 0.48 (0.21 to 1.09) and 2.35 (1.06 to 5.19), respectively.
Among patients aged 12 to 39 years without predisposing comorbidities, the relative risk of heart failure or death was significantly higher for myocarditis associated with COVID-19 than for myocarditis associated with mRNA vaccines (relative risk 5.78 , 1.84 to 18.20).
In conclusion, this study seems to show that myocarditis associated with vaccines is less severe than myocarditis associated with SARS-COV-2 infection. This provides a rational element allowing a more acute understanding of the benefit/risk balance of mRNA vaccines.
To learn more regarding this topic:
COVID-19, vaccines and myocarditis [Dr Florian Zores, cardiologue]
New study: severity of post-vaccination VS post-infection myocarditis in 1 Nordic cohort.
Confirms previous evidence: there is a higher risk of heart failure and death for myocarditis following infection than following vaccination. 1/nhttps://t.co/9wxXnPogQ5 https://t.co/Pbg7U5TGgh— Lonny Besancon ???????? ???????? (@lonnibesancon) February 6, 2023
