COVID-19 vaccine myocarditis tied to fewer adverse events vs. conventional myocarditis
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Key takeaways:
- COVID-19 vaccine-related myocarditis was linked to lower risk for adverse CV events vs. conventional myocarditis.
- Outcomes were similar between vaccine- and COVID-19 infection-related myocarditis.
Clinical outcomes after COVID-19 vaccine-related myocarditis were similar vs. myocarditis from COVID-19 infection, and events were fewer vs. conventional myocarditis, researcher reported.
Vaccine-related myocarditis predominantly affected younger men, whose treatment was similar compared with conventional myocarditis in the months after hospitalization, according to data presented at the International Society for Pharmacoepidemiology Annual Meeting and published in JAMA.
Evaluating postvaccine myocarditis
“Cases of myocarditis have been broadly reported following vaccination with the COVID-19 mRNA BNT162b2 and mRNA-1273 vaccines. Several epidemiological studies confirmed an increased risk of myocarditis shortly after vaccination, predominantly in young adults and after the second dose,” Laura Semenzato, MSc, of the EPI-PHARE scientific interest group in epidemiology of health products from the French National Agency for the Safety of Medicines and Health Products and the French National Health Insurance, and colleagues wrote in JAMA. “Although vaccination resulted in a significant decrease in hospitalization and mortality from COVID-19, it is crucial to evaluate the consequences of postvaccine myocarditis, particularly in young people, who are less likely to have serious illness after SARS-CoV-2 infection and could thus be less inclined toward vaccination.”
In the present study, Semenzato and colleagues evaluated CV complications — hospital readmission for myopericarditis, CV events, all-cause death and a composite of all — related to myocarditis after COVID-19 vaccination compared with SARS-CoV-2 infection over 18 months after initial hospitalization.
Postvaccine myocarditis was defined as myocarditis within 7 days after COVID-19 mRNA vaccination and post-COVID-19 myocarditis was defined as myocarditis within 30 days of SARS-CoV-2 infection.
The analysis included data from 4,635 individuals hospitalized with myocarditis from the French National Health Data System between Dec. 27, 2020, and June 30, 2022.
Vaccine vs. infection vs. conventional myocarditis
Overall, 12% of participants had postvaccine myocarditis, 6% had post-COVID-19 myocarditis and 82% had conventional myocarditis.
Researchers reported that patients with postvaccine myocarditis were younger and more often men (mean age, 26 years; 84% men) compared with those with post-COVID-19 myocarditis (mean age, 31 years; 67%) and conventional myocarditis (mean age, 28 years; 79% men).
Postvaccine myocarditis was associated with lower incidence of the composite clinical outcome compared with conventional myocarditis (weighted HR = 0.55; 95% CI, 0.36-0.86) and was similar compared with post-COVID-19 myocarditis (weighted HR = 1.04; 95% CI, 0.7-1.52), according to the study.
Frequency of medical procedures such as cardiac imaging, troponin assays and stress testing, as well as of drug prescriptions, was similar for all three groups in the 18 months after discharge.
“Part of the lower incidence of all-cause hospitalization observed in postvaccine myocarditis compared with conventional myocarditis might be explained by the more varied etiology of conventional myocarditis cases,” the researchers wrote. “For example, cases linked to inflammatory disease may require more hospital follow-up due to the underlying pathology and have more frequent cardiovascular comorbidities and risk factors. In the current study, no patient with postvaccine myocarditis received a heart transplant and two (0.4%) required extracorporeal membrane oxygenation, which is consistent with other studies.
“The current analyses might suggest a difference in the strength of the association with clinical outcomes by type of mRNA vaccine,” they wrote. “Considering the small number per subgroup, with relatively rare events, further specific studies on this subject are required.”
The researchers noted when the main analysis was repeated with a widened definition of postvaccine myocarditis to include patients with mRNA vaccination in the previous 30 days, a higher risk for postvaccine myocarditis was observed.
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