A research letter published by Diaz and others in the Journal of the American Medical Association on August 4th 2021 reports that there are rare cases of cardiac inflammation following SARS-CoV-2 vaccination.  

They review clinical records of vaccine recipients to identify cases of post vaccination myocarditis or pericarditis.  

Forty hospitals in the United States which were part of the Providence Healthcare system who use the same electronic medical records were included. 

All patients with documented COVID-19 vaccinations administered inside the system who were recorded in state registers at the time were identified.  

Vaccinated patients who subsequently had emergency department or inpatient encounters with diagnoses of myocarditis, myopericarditis or pericarditis were ascertained from the electronic medical records.  The monthly rates of the first time hospital diagnoses were compared.  

Out of 200287 individuals receiving at least one COVID-19 vaccination, 58.9% were women, the median age was 57. 76.5% received more than one dose, 52.6% received the Pfizer, 44.1% received Moderna and 3.1% received the Janssen/Johnson & Johnson vaccine.  Out of these, 20 individuals had vaccine related myocarditis and 37 had pericarditis.

Myocarditis occurred at a median of 3.5 days after vaccination of which:

  • 11 cases were Moderna 
  • 9 cases were Pfizer
  • 15 individuals were male 
  • Median age was 36.  

Four people developed symptoms after the first vaccination and 16 developed symptoms after the second vaccination. 

Nineteen patients had to be admitted to hospital.  All were discharged after a median of two days.  There were no re-admissions or deaths.  Two patients received a second vaccination after the onset of myocarditis and neither had worsening symptoms.  From the last available follow-up, 13 patients had symptom resolution and seven were improving.

Pericarditis developed after the first immunisation in 15 cases and after the second immunisation in 22 cases.  Twelve cases were Moderna, 23 were Pfizer and 2 were the Janssen Johnson & Johnson.  

The median onset was 20 days after the most recent vaccination.  27 individuals were male and the median age 59.  Thirty were admitted to hospital, none to intensive care.  The median stay was one day.  Seven patients with pericarditis received a second vaccination and no patient died.  At the last available follow up, 7 patients had resolved symptoms and 23 were improving. 

Myocarditis and pericarditis are two distinct self-limiting syndromes.  They were observed after COVID-19 vaccination.  Myocarditis developed rapidly in the younger patients, mostly after the second vaccination.  Pericarditis affected older patients later after either the first or second dose.

Some vaccines are associated with myocarditis including mRNA vaccines and the CDC. 

America recently reported the possible association between COVID-19 RNA vaccines and myocarditis primarily in the younger male within a few days of a second vaccination and with an incidence of about 4.8 cases per million.  

The authors of this study show a similar pattern although at higher incidence, suggesting vaccine adverse event under reporting.  

Additionally, pericarditis may be more common than myocarditis amongst older patients. 

Study limitations included that cases might be missed in the outside care setting and there might be a missed diagnosis of myocarditis or pericarditis.

Dr Paul Ettlinger

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