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COVID-19 vaccines and cardiac inflammation

Rarely, cases of myocarditis and pericarditis have been reported after the second dose of mRNA vaccine. It is particularly seen in males under 30 years old. Most cases are mild and patients have recovered quickly.

Myocarditis and pericarditis

There is a link between mRNA COVID-19 vaccines – such as Comirnaty (Pfizer) and Spikevax (Moderna)p– and rare side effects of myocarditis and pericarditis.

  • myocarditis is inflammation of the heart muscle.
  • Pericarditis is inflammation of the pericardium (the thin, sac-like tissue surrounding the heart muscle).

Myocarditis and pericarditis can occur together or separately. 

Myocarditis and pericarditis occur in the general population from a variety of causes. Not all cases that occur after vaccination are caused by the vaccine. Myocarditis and pericarditis can also be caused by COVID-19.

Myocarditis and pericarditis have been reported most in males under 40 years and after the second dose. However, they can happen in any gender and after any dose. Up to date information on cases and rates reported to the Therapeutic Goods Administration (TGA) is available at: www.tga.gov.au/periodic/covid-19-vaccine-weekly-safety-report.

The risk of myocarditis may be higher (although still rare) following Moderna vaccination compared with Pfizer. It is estimated there are around 2 more cases per 100,000 second vaccine doses in Moderna recipients (younger than 40 years) than Pfizer recipients (younger than 40 years). There is no evidence to suggest more severe disease with either vaccine.

Most myocarditis and pericarditis cases linked to mRNA vaccination have been mild and patients have recovered quickly. Longer-term follow-up of these cases is ongoing.

The risk of myocarditis and pericarditis looks much lower in children aged 5-11 years than adolescents. The risk also looks lower after a booster than the primary course.

A longer interval between two doses of the primary course may reduce the likelihood of myocarditis and pericarditis by a small amount. The recommended interval between two doses of an mRNA vaccine is now 8 weeks. The interval can be shortened in some circumstances such as for people with increased risk of severe COVID-19 (to 3 weeks for Pfizer or 4 weeks for Moderna).

Myocarditis and pericarditis after other COVID-19 vaccines

New evidence suggests Vaxzevria (AstraZeneca) may also be associated with a small increased risk of myocarditis and pericarditis. The risk after AstraZeneca looks lower than the risk after Moderna or Pfizer.

The risk of myocarditis and pericarditis after Nuvaxovid (Novavax) is not yet known. A small number of cases were reported in the trial for Novavax but we do not yet know if these were caused by the vaccine.

Guidance for providers

The Australian Technical Advisory Group on Immunisation (ATAGI) and the Cardiac Society of Australia and New Zealand (CSANZ) have jointly developed guidance on managing these conditions. 

The guidance contains advice on assessment, management and follow up. 

COVID-19 vaccination – Guidance on Myocarditis and Pericarditis after mRNA COVID-19 vaccines

This guide provides information on pericarditis and myocarditis following an mRNA COVID-19 vaccine – including Comirnaty (Pfizer) and Spikevax (Moderna).

Risk/benefit profile

ATAGI emphasise that the overwhelming benefits of vaccination in protecting against COVID-19 greatly outweigh the rare risk of these conditions.

All people 5 years and over can be vaccinated against COVID-19 if they do not have any contraindications to the vaccine.

During the consent process, advise people receiving mRNA vaccines:

  • there is a rare risk of myocarditis or pericarditis
  • what symptoms to look out for. 

Pre-existing cardiac conditions

Most pre-existing cardiac conditions are not regarded as contraindications to vaccination. Some patients should consult a GP or cardiologist about the best timing for vaccination and if any additional precautions are needed.

See the guidance document for details. 

Symptoms

Symptoms of myocarditis or pericarditis typically appear within 1 to 5 days of vaccination. People who experience any of these symptoms after having an mRNA COVID-19 vaccine should seek prompt medical attention:

  • chest pain
  • pressure or discomfort in the chest
  • irregular, skipped heartbeats or ‘fluttering’
  • fainting
  • shortness of breath
  • pain when breathing.

Initial investigations for people presenting with symptoms or signs of myocarditis or pericarditis should include ECG, troponin, chest X-ray, and other investigations for other differential diagnoses as clinically indicated.

People who develop myocarditis or pericarditis attributed to their first dose of mRNA vaccine should defer further doses and discuss this with their treating doctor.

Referral to cardiologist

People who experience myocarditis and/or pericarditis after an mRNA COVID-19 vaccine should be referred to a cardiologist for further assessment and management, to investigate for possible causes other than vaccination, and for follow-up.

Last updated: 
29 April 2022

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