The Incidence of Myocarditis and Pericarditis in Post COVID-19 Unvaccinated Patients—A Large Population-Based Study

"Introduction

... It has recently been reported that the incidence of myocarditis and pericarditis is increased in COVID-19 patients during the acute illness. However; whether or not myocarditis and pericarditis after the recovery period are a part of the long COVID-19 syndrome is yet unknown. Herein, we studied the incidence of myocarditis and pericarditis in a large cohort of COVID-19 patients after recovering from the acute infection.

2. Methods

2.1. Study Setting: We retrieved observational data from Clalit Health Services (CHS). CHS is the largest of four health maintenance organizations that offer mandatory health care coverage in Israel...

3. Results

A total of 787,968 Clalit Health Services adult members (age ≥ 18) were included in the study, comprising of COVID-19 cohort (n = 196,992) and a sex and age 3:1 matched control cohort (n = 590,976)...

During the study period, nine cases of myocarditis and 11 cases of pericarditis were detected in the COVID-19 cohort. Twenty-seven cases of myocarditis and 52 cases of pericarditis were detected in the control cohort...

No statistical difference in the incidence rate of both myocarditis (p =1) and pericarditis (p =0.17) was observed between the COVID-19 cohort and the control cohort...

4. Discussion

... Higher risk of myocarditis (risk ratio, 18.28; 95% CI, 3.95 to 25.12; risk difference, 11.0 events per 100,000 persons; 95% CI, 5.6 to 15.8) and pericarditis was observed in a large population study of recently published by Barda et al. Although both our study and the study by Barda et al. are based on Clalit Health Service patients, there are several important differences between the studies. Barda et al. were focused on COVID-19 vaccination, and thus the matching was designed to neutralize vaccination-related factors, while our study is on a non-vaccinated population."