Myocarditis and pericarditis risk with mRNA COVID-19 vaccination compared to unvaccinated individuals: A retrospective cohort study in a Spanish Tertiary Hospital

Abstract

Objective: This study compared the incidence of pericarditis and myocarditis in patients exposed to mRNA COVID-19 vaccines to the incidence in those who were not vaccinated, considering the incidence of these conditions resulting from COVID-19 infection.

Methods: This was a retrospective cohort study of individuals assigned to health area of La Paz University Hospital in Spain. The exposure factor was vaccination with mRNA COVID-19 vaccines between December 27th, 2020 and January 9th, 2022 with a minimum follow-up of one month. The outcome was the incidence of pericarditis or myocarditis in these individuals.

Results: The incidence of pericarditis and myocarditis in the total population exposed to at least one dose of mRNA COVID-19 vaccines was 5/100,000 (CI95%:3 to 8 per 100,000), compared to 70/100,000 (CI95%: 66 to 92 per 100,000) in those who were not vaccinated. In the adolescent population (aged 12-17), the incidence was 10/100,000 in vaccinated population (CI95%: 5 to 45 per 100,000) compared to 20/100,000 in unvaccinated (CI95%: 6 to 79 per 100,000). The incidence of pericarditis or myocarditis in patients with COVID-19 infection was 200/100,000 people (CI95%: 114 to 306 per 100,000). The most common cause of pericarditis and myocarditis in the cohort was idiopathic/infectious (74 cases). Cases of myocarditis attributed to COVID-19 infection were more severe and had higher mortality rates compared to cases with other causes.

Conclusion: The incidence of pericarditis and myocarditis in patients exposed to mRNA COVID-19 vaccines was lower than in those who were not vaccinated, especially in adults.The most common cause of pericarditis and myocarditis was idiopathic/infectious, but the most frequent cause in adolescent patients was mRNA COVID-19 vaccination. Cases of myocarditis due to COVID-19 infection were more severe and had greater mortality.

Keywords: Adverse drug reactions; COVID-19 vaccines; Causality algorithms; Myocarditis; Pericarditis.