In a recent study published in Clinical Infectious DiseasesIn this study, researchers analyzed the incidence of myocarditis among the coronavirus disease 2019 (COVID-19) messenger ribonucleic acid (mRNA)-1273 vaccines.
Various studies have reported a causal relationship between SARS-CoV-2 infection and myocarditis. Furthermore, evidence indicates that myocarditis has occurred among individuals vaccinated with the mRNA-1273 COVID-19 vaccine.
In this study, researchers evaluated the cumulative risk of developing myocarditis or myocarditis among individuals who received the COVID-19 mRNA-1273 vaccine.
The team reviewed reports of suspected myocarditis and myocarditis documented in Moderna’s Global Safety Database between December 18, 2020 and February 15, 2022. Data collected from this database included adverse events reported by individuals globally. The team inquired about the database of valid cases reporting myocarditis and myocarditis. Available references were used to develop a systematic approach characterizing potential reports of myocarditis after mRNA vaccination and assessing causality.
The Brighton Collaboration’s case definition for myocarditis was used to categorize individual cases into five categories: (1) level 1- end-state, (2) level 2- probable case, (3) level 3- probable case, (4) level 4- An event reported with insufficient evidence; and (5) level 5 – not a case of myocarditis or myocarditis based on diagnostic evidence and clinical findings. The team also used the WHO’s Standard Case Causality Assessment Tool – Uppsala Surveillance Center to assess the possibility of a condition causally linked to the vaccine.
The global proportion of mRNA-1273 vaccines was estimated according to data retrieved by the Centers for Disease Control and Prevention (CDC), the European Centers for Disease Control, the Public Health Agency of Canada, the Swiss Federal Office of Public Health, and our data scientist on February 16, 2021.
The team estimated that between December 18, 2020 and February 15, 2022, 568,668,391 doses of the mRNA-1273 COVID-19 vaccine were administered, and 477,932 individual cases were reported, including 181,9802 adverse events. Reported individual cases included 3,027 cases of myocarditis or myocarditis. Of these, 72% of cases were reported by a healthcare professional involved in treating the patient, and 97.5% had serious adverse events, including 1.5% who reported a fatal outcome. Nearly 21% of cases reported recovering from COVID-19, while 1.6% recovered with complications and 25.7% recovered.
The team noted that 40.3% of the total cases were from the European Economic Area (EEA), 25.2% from the United States, 11.5% from Asia, 5.1% from Switzerland, 8.5% from the United Kingdom, 8.8% from Canada, and less From 1% from the Middle East and Australia. The median age of the study population was 29 years, while 75% of cases were reported in men.
The results of the study showed that the number of cases of myocarditis or myocarditis corresponds to an overall reporting rate of 9.23 per 100,000 person-years, regardless of the time of disease onset. The observed reporting rate among individuals who received the mRNA-1273 vaccine varied significantly with respect to age and gender.
Furthermore, the reporting rate for males was 14.54 per 100,000 person-years, and for females it was 4.11 per 100,000 person-years. Across different age groups, the reporting rate was 29.29 per 100 000 person-years among individuals aged 18 to 24 years. When adjusted for age and sex, younger males <40 years of age had the highest reported rates of myocarditis or myocarditis. Overall, the reported reported rates of myocarditis or myocarditis vaccine after mRNA-1273 vaccination resulted in an average rate of 1.03.
When the study was limited to cases reported within seven days of a known COVID-19 dose, the observed reporting rate for vaccines per 100,000 doses was higher after the second vaccine dose was administered. The highest rates reported within seven days of vaccination after the second dose were observed among males aged <39 years, specifically those aged 18–24 years. Comparison of observed and expected rates yielded an average rate of 8.88 for males aged 18–24 years within seven days of the second vaccine dose. The team noted that rates were lower after the third dose than after the second dose.
Overall, the study results showed that myocarditis, or myocarditis, was a rare event in recipients of the COVID-19 mRNA-1273 vaccine. Researchers believe that the benefits of the mRNA-1273 vaccine outweigh the potential risks of vaccine-related myocarditis.