‘Benefits outweigh risk’
In an accompanying editorial in JAMA Cardiology, three doctors from the CDC cite several other reports of myocarditis after mRNA COVID vaccination. These include a case report published in Pediatrics of seven male adolescents aged 14-19 years who presented with myocarditis or myopericarditis within 4 days after receipt of a second dose of the Pfizer vaccine.
But the editorialists noted that the most comprehensive data about the risk for myocarditis following immunization with mRNA vaccines comes from Israel.
The Israeli Ministry of Health recently posted data describing 121 myocarditis cases occurring within 30 days of a second dose of mRNA vaccine among 5,049,424 persons, suggesting a crude incidence rate of approximately 24 cases per million.
On the current case reports, the CDC doctors wrote: “The striking clinical similarities in the presentations of these patients, their recent vaccination with an mRNA-based COVID-19 vaccine, and the lack of any alternative etiologies for acute myocarditis suggest an association with immunization.”
They said that acute onset of chest pain 3-5 days after vaccine administration, usually after a second dose, is a typical feature of reported cases and suggests an immune-mediated mechanism.
But SARS-CoV-2 infection also causes cardiac injury which may result in severe outcomes, and based on currently available data, myocarditis following immunization with current mRNA-based vaccines is rare.
“At present, the benefits of immunization in preventing severe morbidity favors continued COVID-19 vaccination, particularly considering the increasing COVID-19 hospitalization rates among adolescents reported during spring 2021,” the editorialists stated.
But they added that many questions remain. These include whether modifications are needed to the vaccine schedule among persons with a history of possible or confirmed myocarditis after COVID vaccine, how should postvaccine myocarditis be managed, how often should follow-up assessments be performed, how might follow-up assessments affect recommendations to avoid vigorous physical activity following the diagnosis of myocarditis, and do all likely cases of acute myocarditis that appear to be uncomplicated require cardiac MRI for more definitive diagnosis?
“While the data needed to answer such questions are being collected, there is an opportunity for researchers with expertise in myocarditis to develop a comprehensive, national assessment of the natural history, pathogenesis, and treatment of acute myocarditis associated with receipt of mRNA-based COVID-19 vaccines,” they concluded.
In a second editorial in JAMA Cardiology, a group of editors from the journal acknowledged that publication of the current case reports may contribute to additional public concern regarding immunization. But they added that clinicians discussing immunization with patients should recognize that these case series suggest that the symptomatic events consistent with myocarditis are still very rare and appear to be self-limiting.
“Given the risks of COVID-19, including the risk of myocarditis from COVID-19 infection, the editors do not believe these case reports are sufficient to interrupt the march toward maximal vaccination against SARS-CoV-2 as expeditiously as possible,” they said.
A version of this article first appeared on Medscape.com.