Yet another study, this time in Japan, raises concerns about mRNA COVID-19 vaccine safety signals. Recently posted in the preprint server medRxiv, co-author Rokuro Hama, director of the Japan Institute of Pharmacovigilance, a Japanese post-approval monitoring agency, reports evidence of growing concern. A sophisticated operation, this Japanese group diligently pursued its mission. They report that myocarditis mortality ratios (MMRRs) and their confidence intervals (95%) after receiving the COVID-19 vaccines compared with the general reference population over the past three years were significantly higher not only among the young adult population (highest in the 30s with MMRR of 6.69) but also in the elderly. A bombshell finding, the authors in Japan report that myocarditis risk among COVID-19 vaccinated may be four times higher than the apparent MMRRs considering healthy vaccinee effect. They declare, “Underreported post-vaccination deaths should also be considered as suggested by the extremely high myocarditis mortality odds ratio (205.60; 133.52 to 311.94 ).”

The Study

This real-world investigation compares the myocarditis mortality rate in the SARS-CoV-2 vaccinated with that in the general population in Japan. The study was based on the materials and the vital statistics disclosed by the Japanese government

This Japanese study is still in preprint involving 99,834,543 individuals aged 12 and up who had received a COVID-19 vaccine once or twice by February 2022. The authors report the reference population as those aged 10 and above from 2017 to 2019.


The authors report in medXriv that the number of myocarditis deaths meeting inclusion criteria were 38 cases. MMRR (95% 16 confidence interval) was 4.03 (0.77 to 13.60) in 20s, 6.69 (2.24 to 16.71) in 30s, 3.89 (1.48 to 8.64) 17 in 40s, respectively. SMR of myocarditis was 2.01 (1.44 to 2.80) for the overall vaccinated population, and 1.65 (1.07 to 2.55) for those 60 years or older. Estimated adMMRRs and adSMR were about 4 times higher than the MMRRs and SMR. Pooled MOR for myocarditis was 205.60 (133.52 to 311.94).


The results of this study raise bombshell implications. SARS-CoV-2 vaccination was associated with a higher risk of myocarditis death, not only in young adults but also in all age groups including the elderly. Considering the healthy vaccinee effect, the authors suggest that the risk of this serious adverse event could be four times or higher than the apparent risk of myocarditis death. Importantly they emphasize that any underreporting must also be considered. Based on this study, the risk of myocarditis following SARS-CoV-2 24 vaccination may be more serious than that reported previously. This study dovetails with other evidence that the safety of vaccines must be reconsidered. 

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