Study Links Risk of Myocarditis with Pfizer Vaccination but Finds Even Higher Risk of Myocarditis Following COVID Infection

August 26, 2021

A real-world case-control study from Israel, published yesterday, studied cohorts of individuals vaccinated with the Pfizer COVID-19 mRNA vaccine and unvaccinated individuals who became infected with SARS-CoV-2 for adverse effects. The vaccination cohorts included a mean of 884,828 vaccinated persons, with a median age of 38 years, and the SARS-CoV-2 infection cohort had a total of 173,106 persons with a median age of 34 years.

They found that the vaccinated cohort was associated with an increased risk of myocarditis (2.7 events per 100,000 persons) as well as lymphadenopathy (78.4 events per 100,000 persons), appendicitis (5.0 events per 100,000 persons), and herpes zoster infection (15.8 events per 100,000 persons). Researchers noted that vaccination was “substantially protective against adverse events such as anemia, acute kidney injury, intracranial hemorrhage, and lymphopenia.”

However, it should be noted that in a separate cohort*, an even higher risk of myocarditis was found to be associated with SARS-CoV-2 infection (11.0 events per 100,000 persons), in addition to other cardiovascular complications including acute kidney injury (125.4 events per 100,000 persons), pulmonary embolism (61.7 events per 100,000 persons), and intracranial hemorrhage (7.6 events per 100,000 persons).

* The researchers pointed out that “the effects of vaccination and of SARS-CoV-2 infection were estimated with different cohorts. Thus, they should be treated as separate sets of results rather than directly compared.”