Myocarditis is an inflammatory disease of the heart muscle, whilst pericarditis is an inflammatory disease of the lining of the heart muscle. They are rare conditions, most commonly associated with viral infections (including SARS-CoV-2) but can also be triggered by other factors such as medications and autoimmune conditions.

Globally, an increased number of cases above an expected population rate of myocarditis and pericarditis have been reported in individuals who have received mRNA COVID-19 vaccines (eg. Comirnaty™ and Moderna).

How is myocarditis /pericarditis triggered following mRNA vaccination?

The exact mechanism behind cardiac inflammation temporally associated with a COVID-19 mRNA vaccine is currently being investigated. Clinical causes from international surveillance data suggest an immune-mediated or hypersensitivity trigger.

Who is at risk of myocarditis/pericarditis?

Myocarditis and pericarditis from any cause, occurs more commonly in males than females. It is more likely to affect younger adults.

Reported rates of myocarditis and pericarditis occurring following administration of an mRNA COVID-19 vaccine vary; however, they are above expected background rates. International vaccine safety surveillance data currently suggests that it is more commonly associated with administration of a second dose than the first dose.

Pre-existing cardiac conditions and mRNA vaccination

Individuals with the following cardiac conditions can safely receive COVID-19 mRNA vaccines without the need for additional monitoring or precautions:

  • Coronary artery disease
  • Myocardial infarction
  • Stable heart failure
  • Arrhythmias
  • Rheumatic fever
  • Rheumatic heart disease
  • Kawasaki disease
  • Most congenital heart disease
  • Those with implanted cardiac devices

Those with a history of the following conditions can also receive COVID-19 mRNA vaccines; however should consult their treating specialist to determine the appropriate timing for vaccination:

  • Inflammatory cardiac conditions (including myocarditis and pericarditis)
  • Current acute rheumatic fever
  • Those aged 12-29 years with dilated cardiomyopathy
  • Complex or severe congenital heart disease including single ventricular circulation
  • Acute decompensated heart failure
  • Cardiac transplant recipients

What are the symptoms of myocarditis/pericarditis?

Myocarditis and pericarditis present similarly, with a range of symptoms including:

  • Pain with breathing
  • Chest pain, pressure or discomfort
  • Shortness of breath
  • Palpitations
  • Syncope (faint)

In individuals who have received COVID-19 mRNA vaccines, symptoms have most commonly been reported within 4-5 days of vaccination.

How is myocarditis/pericarditis after COVID-19 vaccination diagnosed and investigated?

If there is suspicion of either of these conditions, especially in adolescents or young adults, timely medical review by a GP or presentation to the emergency department (with cardiology involvement) is important. Additional tests can then be performed to confirm the diagnosis. This includes:

  • blood tests for cardiac biomarkers, such as troponin
  • electrocardiogram (ECG)
  • chest X-ray (CXR)
  • inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)

In the setting of a normal ECG, troponin and inflammatory markers, myocarditis and pericarditis are unlikely. However, if symptoms persist, cardiologist advice is recommended.

In suspected cases, cardiologist input for evaluation and management encompassing other imaging tests such as an echocardiogram is suggested. For confirmed cases, avoidance of high-intensity exercise until symptoms have resolved is recommended.

It is also important that all other potential causes of myocarditis/pericarditis are excluded. Thus, testing for other viral aetiologies (eg. enterovirus, respiratory viral pathogen testing etc) as well as previous SARS-COV-2 infection (PCR and serology/antibody testing) is recommended.

How is myocarditis/pericarditis after COVID-19 vaccination treated?

Current data shows that most cases of myocarditis/pericarditis following COVID-19 mRNA vaccination have mild symptoms and recover well. Information on long term sequelae is not yet available.

Treatment of these conditions is managed by a cardiologist and include supportive therapies, often with anti-inflammatory medication. In the rare severe or complicated cases, specific management for arrythmias, decreased cardiac function or congestive cardiac failure with pharmacological agents such as ACE-inhibitors and beta-blockers or mechanical support may be necessary.

Implications on future vaccine doses

For individuals where the cause of inflammation is attributed to COVID-19 mRNA vaccination, referral to a cardiologist is recommended. At this time, ATAGI recommends that further doses of COVID-19 mRNA vaccines are deferred until further safety data is available.

What is the risk/benefit ratio for vaccination for the young adult age group?

It is important to discuss your individual circumstances with a health care provider in order to make an informed decision.

The level of COVID-19 community transmission in Australia can change quickly. Factors to consider include age, potential for exposure to the virus (including in the workplace), high rates of global transmission, the emergence of new variants of the virus, as well as the potential for future changes to Australia’s border controls.

Whilst COVID-19 infection can sometimes result in myocarditis/pericarditis, its incidence following COVID-19 vaccination is comparatively extremely rare. Most individuals diagnosed with myocarditis/pericarditis following COVID-19 vaccination have responded well to treatment.

Resources

Authors: Rachael McGuire (MVEC Education Nurse Coordinator), Francesca Machingaifa (MVEC Education Nurse Coordinator), Daryl Cheng (MVEC Medical Lead) and Nigel Crawford (Director SAEFVIC, Murdoch Children’s Research Institute)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator) and Daryl Cheng (MVEC Medical Lead)

Date: 4 August, 2021

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.