The risks of myocarditis associated with the COVID-19 vaccination are explained

Study: Long-term prognosis of patients with myocarditis attributable to COVID-19 mRNA vaccination, SARS-CoV-2 infection, or conventional etiologies. Image credit: SrideeStudio / Shutterstock.com

Nationwide study reveals that while myocarditis linked to COVID-19 mRNA vaccines has less severe long-term outcomes, young, healthy men may still face months of follow-up and medical management, raising critical considerations for future vaccine recommendations.

In a recent study published in JAMA Network, Researchers are determining whether messenger ribonucleic acid (mRNA) vaccines for coronavirus disease 2019 (COVID-19) increase the risk of myocarditis.

COVID-19 and myocarditis

Myocarditis is a common and potentially serious medical condition caused by inflammation of the myocardium, the muscle tissue of the heart. It is characterized by a decrease in the blood-pumping efficiency of the heart and symptoms such as chest pain, shortness of breath, and fast or irregular heartbeats.

Although myocarditis often resolves on its own, severe cases may require months or even years of medical intervention to resolve, resulting in significant debilitation and financial burden for patients and their families.

Observational studies have suggested an association between the mRNA-1273 and BNT162b2 COVID-19 vaccines and an increased incidence of myocarditis, with one report finding a 30-fold increased risk after the second dose of mRNA-1273.

However, studies aiming to establish an association between vaccination against COVID-19 and myocarditis lack sufficient follow-up time after disease diagnosis and have failed to address myocarditis severity or management from different origins.

Since COVID-19 is associated with an increased risk of myocarditis and vaccines have been shown to significantly reduce the risk of COVID-19 and improve outcomes after COVID-19, understanding the effects of vaccination against COVID-19 will allow clinicians and policymakers to clarify the benefits and potential risks associated with vaccinations in relevant demographics.

About the study

The present study aims to examine the incidence of myocarditis and subsequent cardiovascular complications after vaccination and COVID-19. The researchers also looked at long-term disease management 18 months after disease onset in terms of the number of drug prescriptions and medical procedures.

Data for the study were obtained from the French National Database of Hospital Discharges (PMSI), the National Health Data System (SNDS), the French National Vaccination Database for COVID-19 (VAC-SI) and severe coronavirus 2 acute respiratory syndrome (SARS-COV- 2) diagnosis test database (SI-DEP), which collectively includes the entire French population of 67 million people. The International Classification of Diseases and Related Health Problems, 10^u Revision (ICD-10) codes were used to define and identify both myocarditis and COVID-19.

The study’s data collection was limited to December 2020 to June 2022 and only included people between the ages of 12 and 49. For the analysis, study participants were classified as having post-vaccination myocarditis if they were hospitalized within seven days of the COVID-19 mRNA vaccination or post-COVID-19 myocarditis if they were hospitalized within 30 days of the diagnosis of COVID-19 without prior immunization. Conventional myocarditis included patients diagnosed with myocarditis of any other origin.

Data collection included demographics, vaccination status, medical history, medical procedures, hospital visits or drug prescriptions after the diagnosis of myocarditis. Incidence and outcomes of myocarditis were assessed through Cox regression models, weighted for type of myocarditis. The risk of developing myocarditis was modeled using multinomial multivariate logistic regression models adjusted for sociodemographics and comorbidities.

Study findings

During the study period, 4,635 people were hospitalized for myocarditis, 12% of which were classified as post-vaccination, 6% as post-COVID-19, and 82% as conventional myocarditis. About 67% of patients with post-vaccination myocarditis developed symptoms after the second dose of vaccination.

Assessments of myocarditis type revealed that patients with post-vaccination myocarditis were younger, with a mean age of 25.9 years, and more likely to be men with a lower history of chronic disease compared with conventional myocarditis. In contrast, patients with post-COVID-19 myocarditis were older with a mean age of 31 years, more likely to be diagnosed with comorbidities, and less often male at 67% compared to 84% of patients with post-vaccination myocarditis.

Clinical outcomes over 18 months of follow-up were more severe in the post-COVID-19 and conventional myocarditis cohort, both resulting in mortality rates of 4% compared with 0.2% in the post-vaccination group. Hospitalization reports showed similar trends, with 5.8%, 4%, and 3.2% of conventional, post-COVID-19 and post-vaccination patients requiring hospitalization, respectively. However, the drugs and medical procedures in all cohorts were not statistically different from each other.

conclusions

Although vaccination with COVID-19 mRNA was associated with an increased incidence of subsequent myocarditis compared with other causes of disease, subsequent clinical outcomes, including mortality, were significantly reduced in this cohort. The current study identified younger male subjects, especially those who received the second dose of mRNA vaccine, as the highest-risk population, thus highlighting the need for preventive clinical monitoring between seven and 30 days after vaccination.