Possible mRNA vaccine link with heart muscle inflammation

By Melissa Coade

Wednesday June 30, 2021

There might be link between inflammation of the heart muscle and COVID vaccines. (twinsterphoto/Adobe)

Two international studies have identified a possible link between the rare incidence of heart muscle inflammation with a shot of one of the COVID-19 mRNA vaccines (Pfizer or Moderna) — but medical experts maintain these types of vaccines have proven to be ‘highly effective’ in preventing disease and pose a much smaller health risk than the virus itself.

The two separate studies were published in the Journal of the American Medical Association (JAMA) on Wednesday and documented cases of patients who had experienced acute myocarditis – an inflammation of the heart muscle – within five days of having received either the Pfizer or Moderna COVID-19 vaccines.

The first study was led by researchers from the Walter Reed National Military Medical Centre in Maryland and reviewed 23 patients within the military health system. 

The other study, led by Dr Raymond Kim from Duke Cardiovascular Magnetic Resonance Centre in North Carolina, described four patients who presented with acute myocarditis after receiving a mRNA COVID-19 shot.

Young male adults from the study’s subgroup experienced more cases of the condition than female patients, and medical experts recommend that any person who experienced acute chest pain within the first few days of receiving their mRNA vaccine should see a doctor straight away.

Cardiologist and University of Sydney Professor Chris Semsarian stressed the research did not imply causation.

“The complication of myocarditis is exceedingly rare in these two studies – 27 cases (23+4) amongst over 3 million vaccinated,” Semsarian said.

“The studies should remind clinicians that all vaccines have rare complications, and in this case, cardiac symptoms such as chest pain or shortness of breath should be investigated if they occur post-vaccination.”

Dr Roger Lord from the Australian Catholic University’s faculty of health sciences added that in the second study of four patients, subjects had recorded elevated white blood cell counts upon their admission to hospital – potentially indicating that they were also battling another type of infection.

“Testing for COVID-19 infection and other respiratory viruses indicated a negative response, however the possibility of infection with other pathogens to account for elevated WBC was not determined,” Lord explained.

“The authors clearly establish the development of myocarditis in the four patients but later indicate that methods for testing for COVID-19 infection or other respiratory viruses were not fool proof and that the development of myocarditis with non-mRNA COVID-19 vaccines remains unknown.” 

Dr Daryl Chen from the Melbourne Vaccine Education Centre said it was important to maintain perspective that risk of rare events such as acute myocarditis paled into comparison to the potentially debilitating effects of being infected by the COVID-19 virus.

These rare adverse events pale in comparison to the serious long term cardiac injury and morbidity that is caused by SARS-CoV-2 infection.

“Thankfully, the overwhelming majority of overseas reported cases thus far have been mild and have made a rapid recovery,” Dr Chen said.

Lord’s view on the chances of an individual developing an inflammation of the heart muscle after receiving one of the mRNA vaccines is that it is ‘extremely rare’.

“This adverse event may involve other factors such as an underlying infection to initiate the process,” he said. 

According to Chen, this latest research from the US demonstrates how Australian and international vaccine safety surveillance systems are constantly adapting to the latest available data. This includes the emergence of new information about mRNA vaccines, such as myocarditis, which was not evident at the clinical trial stage.

“Australians want to know that our rollout is underpinned by a robust safety vaccine system, and any previous and future changes to the rollout system should be viewed in this context,” Dr Chen added, pointing to the Therapeutic Goods Administration and other state-based agencies charged with identifying and providing information for groups like the Australian Technical Advisory Group on Immunisation (ATAGI) as reliable systems that helped decision-makers ‘come to clinical safety decisions.

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