COVID-19 vaccines and cardiac inflammation

Cases of myocarditis and pericarditis after COVID-19 vaccines are rare: mostly reported in males under 40 years of age, after the second dose. Cases do occur in both females and males, at any age, and after any dose, including a third or fourth dose. Most cases are mild and patients recover quickly.

Myocarditis and pericarditis

There is a link between COVID-19 vaccines 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.

The risk of myocarditis is highest in people aged 16 to 30 years (peak 16 to 18 years), and is higher in males than females.1-3 The risk does not appear to be as high with booster doses compared with dose 2 of the primary course.3,4

Up-to-date information on cases and rates reported to the Therapeutic Goods Administration (TGA) is available in its COVID-19 vaccine safety reports

The risk of myocarditis is higher (although still rare) after vaccination with Moderna original formulation compared with Pfizer original formulation. It is estimated there are around 2 more cases per 100,000 second vaccine doses in people under 40 who received Moderna original formulation than Pfizer original formulation.

Evidence suggests that AstraZeneca and Novavax are probably associated with a small increased risk of myocarditis and pericarditis.

This risk after AstraZeneca looked lower than the risk after Moderna original formulation or Pfizer original formulation. The small number of total doses of Novavax given globally prevents the calculation of a precise risk as of February 2023.

ATAGI will continue to monitor data as it emerges and update advice accordingly.

There is no evidence to suggest myocarditis or pericarditis is more severe following a particular brand of vaccine.

Most myocarditis and pericarditis cases linked to COVID-19 vaccination have been mild and patients have recovered quickly. Longer-term follow-up of these cases is ongoing.

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

In children aged 6 months to less than 5 years, there is no clear attributable risk of myocarditis and pericarditis after COVID-19 vaccines.

A longer interval between doses of the primary course may reduce the likelihood of myocarditis and pericarditis by a small amount. A longer interval may also improve vaccine protection. For information on current recommended intervals and available vaccines, visit the Australian Immunisation Handbook.


The Australian Technical Advisory Group on Immunisation (ATAGI) has 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. 

Risk/benefit profile

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

People aged 6 months 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 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 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.

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.

As of February 2023, the risk of myocarditis or pericarditis after booster doses with Pfizer or Moderna bivalent original/Omicron vaccines has not been fully characterised.

Injection Technique

Some scientific reports have proposed that inadvertent injection of a COVID-19 vaccine into a blood vessel may have been a contributing cause of serious adverse events following immunisation, such as myocarditis and thrombosis with thrombocytopenia syndrome (TTS).

ATAGI has reviewed the available evidence and considers that injection technique is highly unlikely to be a contributor to these adverse events for several reasons:

  • The majority of TTS cases occurred after the first dose of a viral vector vaccine (AstraZeneca). The majority of myocarditis cases occur after the second dose of an mRNA vaccine such as Pfizer or Moderna. If intravascular injection was an important contributor, there would not be a differential distribution of cases by vaccine dose.
  • Direct injection into a blood vessel is unlikely in recommended injection sites.
  • TTS typically occurred some days or even weeks after vaccination, which does not fit with the proposed theory of direct vascular injury which occurs early in animal models.

Based on a review of the available evidence, ATAGI does not recommend routinely aspirating (drawing back) needles before injection. This practice was rejected some decades ago, due to several disadvantages including prolonging the procedure, potentially associated pain, and increasing the risk of needle–syringe disconnection.

Further information on vaccine administration is available in the Australian Immunisation Handbook.


  1. Yauhara J, Masuda K, Aikawa T, et al. Myopericarditis after COVID-19 mRNA vaccination among adolescents and young adults: a systematic review and meta-analysis. JAMA Pediatrics 2023;177:42-52.
  2. Ling RR, Ramanathan K, Tan FL, et al. Myopericarditis following COVID-19 vaccination and non-COVID-19 vaccination: a systematic review and meta-analysis. Lancet Respir Med 2022;10:679-88.
  3. Pillay J, Gaudet L, Wingert A, et al. Incidence, risk factors, natural history, and hypothesised mechanisms of myocarditis and pericarditis following COVID-19 vaccination: living evidence syntheses and review. BMJ 2022;378:e069445.
  4. Yechezkel M, Mofaz M, Painsky A, et al. Safety of the fourth COVID-19 BNT162b2 mRNA (second booster) vaccine: a prospective and retrospective cohort study. Lancet Respir Med 2023;11:139-50.
Date last updated:

Help us improve

If you would like a response please use the enquiries form instead.