Heart Inflammation Risk Following mRNA COVID-19 Vaccination Could Be Common

A new study published by the Journal of the American Medical Association (JAMA) on August 4, 2021, found two distinct self-limited heart-related syndromes, myocarditis, and pericarditis, were observed after COVID-19 vaccination.

The US Centers for Disease Control and Prevention (CDC) vaccine committee reported on June 23, 2021, a possible association between mRNA COVID-19 vaccines and myocarditis, primarily in younger male individuals, within a few days after the second vaccination, at an incidence of about 4.8 cases per 1 million. 

This new study shows a similar pattern, although at higher incidence, suggesting mRNA COVID-19 vaccine adverse event underreporting.

Myocarditis developed rapidly in younger patients, mainly after the second vaccination. 

Additionally, pericarditis may be more common than myocarditis among older patients after either the first or second COVID-19 vaccine dose.

Among 2 million patients of the Providence Health Care System in the western USA receiving at least 1 COVID-19 vaccination, twenty individuals had vaccine-related myocarditis (1.0 [95% CI, 0.61-1.54] per 100,000), and 37 had pericarditis (1.8 [95% CI, 1.30-2.55] per 100,000).

The mean monthly number of cases of myocarditis or myopericarditis during the prevaccine period was 16.9 vs. 27.3 during the vaccine period. 

And the mean numbers of pericarditis cases during the same periods were 49.1 and 78.8, respectively.

Four persons developed myocarditis symptoms after the first vaccination, and 16 developed symptoms after the second.

Myocarditis occurred a median of 3.5 days after vaccination. Seventy-five percent of the individuals were male, and the median age was 36 years.

All patients were discharged after a median of 2 days. There were no readmissions or deaths.

However, pericarditis developed after the first immunization in 15 cases and after the second immunization in 22 patients.

The median onset of pericarditis was 20 days after the most recent vaccination. 

Twenty-seven individuals (73%) were male, and the median age was 59 years. And no patient died.

This study’s limitations include cases missed in outside care settings and missed diagnoses of myocarditis or pericarditis (which would underestimate the incidence), as well as inaccurate EMR vaccination information. 

The temporal association does not prove causation. However, the short span between mRNA COVID-19 vaccination and myocarditis onset, and the elevated incidence of myocarditis and pericarditis in this study, lends support to a possible relationship, wrote these researchers.

CDC continues to recommend COVID-19 vaccination for everyone 12 years of age and older given the greater risk of other serious complications related to COVID-19, such as hospitalization, multisystem inflammatory syndrome in children (MIS-C), or death.   The GACVS COVID-19 subcommittee has reviewed all available information to date, and notes the benefits of mRNA COVID-19 vaccines outweigh the risks in reducing hospitalizations and deaths due to COVID-19 infections.

Finally, it is important to frame concerns about potential vaccine-associated myocarditis within the context of the current pandemic. Infection with SARS-CoV-2 is a clear cause of serious cardiac injury in many patients.11 The mechanism of injury may be direct infection, an immune-mediated response, or a combination of direct or indirect effects. Prevalence of cardiac injury may be as high as 60% in seriously ill patients. Notably, nearly 1% of highly fit athletes with mild COVID-19 infection have evidence of myocarditis on cMRI.

The researchers disclosed various industry relationships. Corresponding Author: George A. Diaz, MD, Providence Regional Medical Center Everett, 1700 13th St, Ste B3-018, Everett, WA 98201 ([email protected]).

Note: A study published by JAMA on June 27, 2021, reported a case series of 23 male patients, including 22 previously healthy military members. Myocarditis was identified within four days of receipt of a COVID-19 vaccine. For most patients (n = 20), the heart-related diagnosis was made after the second dose of an mRNA COVID-19 vaccine.

A non-peer reviewed study in medrxiv.org showed myocarditis (or pericarditis or myopericarditis) from primary COVID19 infection occurred at a rate as high as 450 per million in young males. Young males infected with the virus are up 6 times more likely to develop myocarditis as those who have received the vaccine.

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