Disentangling a Thorny Issue: Myocarditis and Pericarditis Post COVID-19 and Following mRNA COVID-19 Vaccines

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Myocarditis and pericarditis are potential adverse events following immunization (AEFI) with mRNA COVID-19 vaccines.
• Understanding the incidence and characteristics of these AEFI is crucial for vaccine safety monitoring.

Purpose of the Study:

• To describe cases of myocarditis and pericarditis reported in association with mRNA COVID-19 vaccines.
• To compare the risk of these conditions following mRNA COVID-19 vaccination versus SARS-CoV-2 infection and other viral causes.

Main Methods:

• A pharmacovigilance study utilizing data from the Vaccine Adverse Events Reporting System (VAERS) from 1990 to July 2021.
• Inclusion of definitive, probable, and possible cases based on Brighton Collaboration Group criteria.
• Comparative risk assessment against smallpox vaccines, SARS-CoV-2 infection, and common viral myocarditis.

Main Results:

• mRNA COVID-19 vaccines were most frequently suspected in reported myocarditis (64.0%) and pericarditis (55.1%) cases.
• Events predominantly affected young males, often after the second vaccine dose with a short onset time.
• The risk of myocarditis/pericarditis post-mRNA COVID-19 vaccination (0.38/100,000) is substantially lower than post-SARS-CoV-2 infection (1000-4000/100,000) or common viral myocarditis (1-10/100,000/year).
• Relative Reporting Odds (ROR) for myocarditis and pericarditis were lower for mRNA COVID-19 vaccines compared to smallpox vaccines.

Conclusions:

• Myocarditis and pericarditis following mRNA COVID-19 vaccination are rare events, predominantly observed in young males.
• The risk-benefit profile favors mRNA COVID-19 vaccination, as the risk of these cardiac conditions is significantly lower than from natural infection or other viral etiologies.
• Pharmacovigilance systems like VAERS are essential for ongoing monitoring of vaccine safety.