In brief

• Health NZ found no cases of myocarditis after COVID infection.

• Health officials previously claimed myocarditis risk was higher post-infection than post-vaccine.

• New findings suggest more deaths from vaccine-caused myocarditis than COVID-related.

• Questions arise about Health NZ’s research adequacy and diagnostic practices.

Previous claims vs current data

When vaccine-related myocarditis hit the headlines in late 2021, health officials used the news media to reassure the public that the risk of myocarditis was far higher after COVID infections than after the vaccine.

However, in a letter just released to medical lobby group NZDSOS on Friday, Te Whatu Ora says that between 1 January 2020 and 21 June 2024 “There were no events where an individual who was positive for COVID-19 was diagnosed with myocarditis” within 28 days of their infection.

Implications of the new findings

On the face of it, Te Whatu Ora’s statement–  two weeks after climate agency NIWA was pinged for making false statements without first doing the research – means that a second government agency is now caught for shoot-first, research later media spin.

Diagnostic concerns and broader implications

According to Medsafe, New Zealand had a background incidence of diagnosed myocarditis of 90 cases per year, or just under two a week, pre-pandemic. 

Myocarditis is like a floating iceberg, 90% of cases are fleeting and never diagnosed. Only the most serious cases turn up in hospital, usually because someone has done strenuous exercise while their heart muscle was inflamed, and they developed chest pain, heart palpitations or breathlessness that worried them enough to seek medical attention.

At a background level of roughly two serious cases a week, frankly it’s surprising that none of those people had COVID in the previous 30 days given that almost the entire population has now had it. Also, international studies have shown COVID patients have a five times higher risk of myocarditis than people who have not had COVID the previous year(note the study did not discuss the vaccine).

If a GP suspects myocarditis the patient is referred to hospital for cardiologist assessment. The OIA was robust enough to catch all serious cases.

If the pre-COVID background incidence has risen from 90 cases per five million people, and COVID is not the culprit, some fairly serious questions will be asked.  Centrist is lodging an OIA to find out the myocarditis background rate for each year since 2020. 

We are not suggesting the answer is necessarily the vaccine, although it could be. The answer could easily be at least partially explained by what appears to be  good evidence that NZ is not diagnosing myocarditis as well as other countries, but that is a story for another day.

Comparing global and local myocarditis rates

There’s evidence that New Zealand is not diagnosing myocarditis as well as other countries. 

Studies completed before the COVID vaccine was rolled out in early 2021 show the global myocarditis rate was between 10 and 22 cases per 100,000 population. Some studies say it’s even higher. 

That means NZ’s five million (50 x 100K) should be recording between 500 and 1100 cases per year, pre-pandemic, not 90.

Underdiagnosis in New Zealand

If NZ is diagnosing at a rate 5 to 10 times lower than other western countries, when there’s absolutely no evidence that we are 5 to 10 times healthier, it suggests we are not looking for myocarditis that’s happening in front of us.

International perspectives on myocarditis 

As a European/Canadian study submitted mid January 2021, when the global vaccine release was literally in its first days and young people had not been jabbed, myocarditis was already the leading cause of sudden cardiac death in young people: “Nowadays, the prevalence of myocarditis has been reported from 10.2 to 105.6 per 100,000 worldwide, and its annual occurrence is estimated at about 1.8 million cases. 

This wide range of reported cases reflects the uncertainty surrounding the true prevalence and a potential underdiagnosis of this disease. Since myocarditis continues to be a significant public health issue, particularly in young adults in whom myocarditis is among the most common causes of sudden cardiac death, improved diagnostic and therapeutic procedures are necessary.”

Challenges in diagnosing myocarditis 

A 2019 study, clearly untainted by either COVID or vaccines, also spelt out how medics won’t find myocarditis unless they look:

“The presentation pattern of viral myocarditis can range from nonspecific symptoms of fatigue and shortness of breath to more aggressive symptoms that mimic acute coronary syndrome. After the initial acute phase presentation of viral myocarditis, the virus may be cleared, resulting in full clinical recovery; the viral infection may persist; or the viral infection may lead to a persistent autoimmune-mediated inflammatory process with continuing symptoms of heart failure. As a result of these 3 possibilities, the diagnosis, prognosis, and treatment of viral myocarditis can be extremely unpredictable and challenging for the clinician.”

Assessing the true impact of myocarditis 

In theory, if NZ is still using the same criteria to detect myocarditis as it was using pre-pandemic to find the extremely low 90 cases a year, any increase in that rate since 2020 could easily be blamed on the vaccine. In theory.

In practice, given the huge increase in myocarditis awareness since the pandemic, it’s likely that far more people are getting checked now. But based on overseas rates NZ should have been reporting 500 to 1100 cases a year pre-pandemic, not 90.

So the real clue will not be whether our case numbers now exceed 90, but whether they exceed the upper background projection of 1100.

Nearly ten million vaccine doses were delivered in NZ. If vaccine myocarditis is a real concern, it should show up in the next OIA release now that Te Whatu Ora has backed itself into a corner.