A new study published in JAMA shows 1 in 100,000 people had vaccine-related myocarditis and 1.8 in 100,000 people had pericarditis — compared to the CDC’s data that 4.8 people per 1 million suffer myocarditis after receiving a COVID vaccine.
U.S. public health officials claim cases of myocarditis and pericarditis following COVID vaccination are rare — but new research published online in the Journal of American Medical Association (JAMA) shows they may happen more often than reported.
Post-vaccine myocarditis and pericarditis also appear to represent two “distinct syndromes,” Dr. George Diaz, with the Providence Regional Medical Center Everett, told Medscape Cardiology.
The records, obtained from 40 hospitals in Washington, Oregon, Montana and California, showed 20 people had vaccine-related myocarditis (1.0 per 100,000) and 37 had pericarditis (1.8 per 100,000).
A recent report, by the Centers for Disease Control and Prevention (CDC), based on data from the Vaccine Adverse Events Reporting System (VAERS), suggested an incidence of myocarditis of about 4.8 cases per 1 million following receipt of an mRNA COVID vaccine.
The median age of the CDC report’s cohort was 57 years, and 59% were women. Only 77% received more than one dose. Fifty-three percent received Pfizer, 44% Moderna and 3% received Johnson & Johnson’s (J&J) COVID vaccine.
Myocarditis is inflammation of the heart muscle that can lead to cardiac arrhythmia and death. According to researchers at the National Organization for Rare Disorders, myocarditis can result from infections, but “more commonly the myocarditis is a result of the body’s immune reaction to the initial heart damage.”
The new JAMA study showed a “similar pattern [to the CDC study], although at higher incidence [of myocarditis and pericarditis] after vaccination, suggesting vaccine adverse event under-reporting.”
The JAMA report also stated: “Additionally, pericarditis may be more common than myocarditis among older patients.”
“Our study resulted in higher numbers of cases probably because we searched the EMR, and [also because] VAERS requires doctors to report suspected cases voluntarily,” Diaz told Medscape. Also, in the governments’ statistics, pericarditis and myocarditis were “lumped together,” Diaz said.
According to Tracy Høeg, physician, epidemiologist and associate researcher at UC Davis, the results of the JAMA study are telling, as recent rates correlate with vaccination.
“An important thing I would say is COVID itself does not appear to be correlated with an uptick,” Høeg said in a tweet.
'A telling figure looking at myocarditis rates at 40 hospitals in the Western US w/ recent rates correlated w/vaccination. An important thing I would say is COVID itself does not appear to be correlated with an uptick.'
The researchers calculated the average monthly number of cases of myocarditis or pericarditis during the pre-vaccine period of January 2019 through January 2021 was 16.9 compared with 27.3 during the vaccine period of February through May 2021.
The mean numbers of pericarditis cases during the same periods were 49.1 and 78.8.
The authors said limitations of their analysis include potential missed cases outside care settings and missed diagnoses of myocarditis or pericarditis, which would underestimate the incidence, as well as inaccurate EMR vaccination information.
“Temporal association does not prove causation, although the short span between vaccination and myocarditis onset and the elevated incidence of myocarditis and pericarditis in the study hospitals lend support to a possible relationship,” the authors wrote.
Myocarditis more common in men
The 20 myocarditis cases occurred a median of 3.5 days after vaccination. Eleven occurred after receiving Moderna’s vaccine and nine occurred after Pfizer. Fifteen cases were in men, and the median age was 36 years.
Four individuals developed myocarditis symptoms after the first vaccination (20%) and 16 (80%) after the second dose. Nineteen patients (95%) were admitted to the hospital and were discharged after a median of two days. None of the 20 patients died.
At last available follow-up (median, 23.5 days after symptom onset), 13 patients (65%) had a resolution of their myocarditis symptoms and seven (35%) were improving