Myocarditis and pericarditis are both conditions that can interfere with the heart’s normal function and ultimately compromise the ability to pump blood effectively.1 These disorders can be caused by autoimmune responses, viral infections, and certain medications or toxins.2 While mild cases often resolve on their own, severe cases can lead to hospitalizations, chronic heart issues, and sudden cardiac arrest.3

Since the beginning of the COVID-19 pandemic, both myocarditis and pericarditis have been associated as potential complications of the SARS-CoV-2 infection.4 COVID-19 can provoke a strong immune response in some patients that leads to inflammation of the heart and surrounding tissues.5 Studies have found that a SARS-CoV-2 infection increases the risk of myocarditis and pericarditis outcomes, especially in the middle aged and elderly populations and those with severe illness and comorbidities.6,7,8 Research has also suggested that even individuals with mild COVID-19 symptoms can develop inflammation of the heart, raising concerns about the potential long-term cardiovascular effects.9

After the rollout of the mRNA-based COVID-19 vaccines, cases of myocarditis and pericarditis after vaccination were reported.10 Cases of myocarditis after vaccination were most common in adolescent and young male populations, especially after the second dose.11 Additionally, while myocarditis is a risk associated with the mRNA vaccines, the risk of myocarditis from COVID-19 infection is reportedly much higher.12 Vaccine-associated myocarditis may be milder than infection-associated myocarditis,13,14 but it is unknown whether the differences are due to underlying differences in study participants or because of etiological differences between the vaccine and virus. While many studies have investigated the incidence of myocarditis in COVID-19 infected and vaccinated individuals, few have characterized the relative risk within the same population. Many studies have reported myocarditis incidence in only COVID-19 vaccinated individuals or only SARS-CoV-2 infected individuals. Additionally, the incidence rates vary greatly from study to study providing a lack of clarity on true risk.

The aim of this study was to evaluate the current literature on myocarditis and pericarditis incidence rates after both COVID-19 infection and vaccination and assess the methodology and conclusions of each study. We specifically looked at studies that included both vaccinated and infected cohorts coming from the same population.